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Ⅰ IntroductionAn operational amplifier, or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. Learn more about the most common opamp basics, essential knowledge when selecting and using an op amp in electronics. We can conclude our section and look at Op Amp basics with the following properties and questions. Opamp Basics: Op-Amp CircuitsCatalogⅠ IntroductionⅡ Amplifier Figures of MeritⅢ Q & AⅣ Application: LM358 Classic CircuitsⅡ Amplifier Figures of MeritNegative FeedbackIt is a important technique to improve bandwidth and distortion and control gain.Open-loop GainIt refers to the ratio of the voltage change at the output of the amplifier to the voltage change at the input when the amplifier input and output are open. Common-mode Rejection Ratio (dB)It is the ratio of the amplifier's amplification factor of the differential voltage signal to the amplification factor of the common mode voltage signal.Input Current NoiseIt is the equivalent current noise applied in parallel with the input of the noiseless amplifier.Output CurrentIt refers to the current driven by the load at the output of the op amp. It is usually a function: input overdrive, correlation between output voltage and power supply, temperature, source, and drain characteristics will differ.Phase MarginIt is the phase shift between an output of the same frequency and an inverting input in an open-loop circuit.Voltage GainIt is the ratio of the change in output voltage to the change in input voltage.Programmable Gain BufferIt can set the gain resistance of the op amp (integrated on the template), and the gain can be set to +1, +2, or -1 through simple external connections.Saturation VoltageIt is the voltage between the collector and emitter of the transistor under saturation conditions. In the saturated state, the emitter-base and collector-base are forward biased, so that the voltage between the collector-emitter is very low.Rise TimeThis refers to the time required for the output voltage to change from 10% of its final value to 90% of its final value.Unity-gain BandwidthIt refers to the frequency at which the amplifier's open-loop gain is equal to one. If the op amp frequency response has a single-pole roll-off, the unity-gain bandwidth is equal to 1UGBW.Strobe “OFF” VoltageThe strobe “OFF” voltage is the minimum voltage at the strobe pulse and is guaranteed not to interfere with the comparator operation.Input Current IndexIt refers to the average of the current drawn from the two input pins. In addition, the input current is also commonly called bias current.Gain Bandwidth ProductIt refers to the product of the amplifier's bandwidth and the gain at which the bandwidth is measured.Large Signal Voltage GainIt refers to the ratio of the change in output voltage to the change in input voltage. This parameter is usually specified at a large output voltage, smaller than the maximum output voltage, which is the typical value under direct current conditions.Offset Voltage Temperature CoefficientIt refers to the average rate of change in offset voltage due to changes in junction temperature within a specified temperature range.Output High VoltageIt refers to the high DC output voltage of the comparator, which produces the high output current. And it is usually related to the totem pole or push-pull output of the comparator.Input Source CurrentIt refers to the maximum output positive current produced under the comparator's push-pull output state.Total Harmonic Distortion (THD)When a pure sinusoidal signal is input to the op amp as Vin (w) = Vpsin (wt):Input harmonic distortion: Vout(w)a1Vpsin(wt)+a2Vpsin(wt)+...+anVpsin(nwt)The expression of THD is: THD(%)=[sqrt(a2xa2+a3xa3+...+anxan)/a1]x100Common-Mode Input Impedance (RINCM)It refers to the ratio of the change in the common-mode input voltage to the change in the input current at the inverting or non-inverting terminal.Output Low VoltageIt refers to a low DC output voltage. The output drive is a low voltage sink current. This specification is usually related to the totem pole or push-pull output of the comparator.Using a CMOS op amp as the output driver, although the circuit works well, but requiring a 1m shielded cable, and the oscillation of the operational amplifier is about 1MHz when there is no input signal. If shorten the cable to 10cm, the oscillation is stable.Some op amps are not suitable for driving capacitive loads directly, such as long shielded cables, which is a capacitive load. In addition, coaxial cables have about 60-100pF capacitance per meter.Harmonic DistortionIt refers to the unwanted spurious signals generated at the amplifier output due to the non-linearity of the signal line. When the input is a sinusoidal signal, these spurious signals will appear as integer times of the input frequency (for example, second harmonic, third harmonic).Output Leakage Current (ILEAKAGE)It means that the current enters the comparator output (the output is driven high). It often appears at the output of open collector and open drain.Power Supply Rejection Ratio (PSRR)It refers to the ratio of the change in the input offset voltage to the change in the power supply voltage, PSRR (dB) = 20log10 (DVOS / DVS)Linear Phase DeviationIt refers to how a closed-loop phase response of an operational amplifier approaches and follows the linear relationship between phase change and frequency in a specific frequency band.-3dbIt refers to the frequency when the value of the small signal output amplitude of the closed-loop amplifier decreases to 3dB.Common-mode Voltage RangeIt refers to the typical value of the voltage range at the input, which determines the performance of the amplifier.Specified Power Supply RangeIt describes the power supply voltage required for the operational amplifier to operate.Output Absorption CurrentIt refers to the highest output negative current of the comparator.Output Voltage SwingIt refers to the maximum peak-to-peak swing of the output voltage under a specific load and power supply voltage.Current FeedbackIt refers to a technology used in current feedback amplifiers whose output signal reflects the value of the current input to the inverting input (transimpedance gain function). In some aspects, this topology has operational advantages over traditional voltage feedback.Closed Loop BufferIt refers to an amplifier with high input impedance and low output impedance and a fixed gain of +1. Its typical applications are used for isolation, increased output drive, capacitive load, etc., in addition, there is no need to set the gain resistance.Closed-loop Gain It is the ratio of the change in the output voltage to the change in the input voltage after the feedback and input network added. Generally, this value is set using an external resistance.Common-mode RangeThe common-mode range, also known as the input voltage range, is a measure of the range of input voltages that the input pins of an op amp can accept. This specification is usually relative to the power supply amplitude.Output ImpedanceIt refers to the ideal series output impedance of the ideal operational amplifier when there is no impedance, which is the approximate output impedance of the op amp measured under AC  conditions.Transient ResponseIt refers to the step function response of the closed-loop system of the amplifier under the condition of small signal (usually less than 100mV).Slew RateWhen given a transition or square wave input, the amount of change in the amplifier's output from one level to another. Typical values are averages of values measured based on a change in total output voltage from 10% to 90%.Response TimeIt is the time interval when the input step function makes the output from the initial value to the logic threshold voltage.Unity Gain FrequencyIt refers to the frequency at which the gain of the voltage feedback op amp is 1 (0 dB). For an ideal operational amplifier, its gain-bandwidth product is equal.Intercept PointIt refers to the output power of the fundamental frequency, which is equal to the power value of the fundamental frequency in the specified distortion term (2nd, 3rd, or 3rd intermodulation).Input Offset CurrentIt refers to the current difference between the two inputs.Voltage OverdriveIt means that a certain amount of input step voltage exceeds the minimum drive input voltage required by the comparator to change from one logic level to the opposite logic level.Differential Gain & Differential PhaseDifferential gain refers to the change in the input and output of the gain, and differential phase refers to the phase change in the input stage. They are video measurements, and are a standard measurement in the broadcasting field to measure relative changes in the interpretation of video signal consistency.Voltage FeedbackA technique used in traditional operational amplifiers, where part of the output voltage is fed back to the input, and the voltage difference between the two inputs is amplified by the operational amplifier. Avol Open-loop Voltage Gain“A” is a sign of gain. The letter “V” written below indicates the gain of voltage, and the letter “ol” also written below is an abbreviation for open loop. Open-loop voltage gain refers to the gain (Vout / Vin) of the amplifier without feedback. Due to the existence of the bias voltage, these errors must be compensated.Logic Threshold VoltageIt refers to the voltage that causes the comparator output state to change when the input offset voltage is exceeded.Output ResistanceIt refers to the value of the series resistance at the output of an ideal op amp with zero output resistance, which measured under DC conditions.Gain FlatnessIt refers to the volume of gains “violently increasing” and “rapidly decreasing” in a given bandwidth range measured in decibels (dB), which affects the most important parameter specifications such as phase margin, gain margin, and closed-loop gain.Offset Current Temperature CoefficientIt refers to the average rate of change in deviation current due to changes in junction temperature within a specified temperature range.Input ImpedanceIt is the ratio of input AC voltage to input AC current.Input Voltage NoiseIt refers to the equivalent voltage noise in series with a noiseless amplifier.Input Offset VoltageIt is the product of the DC error voltage between the inputs and the closed-loop gain, because of the non-ideal balance between the input stage and the output is caused by the DC error voltage of the input terminals.Gain MarginOpen loop gain when the phase between the inverting input and output crosses zero at a certain frequency.Supply CurrentIt refers to the current required from the power supply to the unloaded amplifier and to the power supply at the output midpoint.Settling TimeIt refers to the time between the input step function initial value and the output voltage reaching the specified error band. The error band refers to the percentage of the total voltage change.Differential Input ResistanceIt is the ratio of the change in the input voltage to the change in the input current.Ⅲ Q & AQ1: What is the difference between a voltage feedback amplifier and a current feedback amplifier?A: The internal circuits of these two op amps are different. The voltage feedback op amp is restricted by the internal design, and it only has a very low input bias current, but there is no internal limit on the differential input voltage, because it is limited only when external feedback is required. In contrast, for a current feedback amplifier, its differential input voltage is subject to internal design, but it does not limit its input bias current, so it is limited only when external feedback is required.Q2: What is the difference between open and closed loops?A: The open loop gain is actually the internal gain of the op amp without feedback, and usually takes any value between 1,000 and 10,000. Closed loop gain is the gain of the entire circuit, which is equal to the open loop gain divided by 1 plus the loop gain (the improvement coefficient). In fact, the gain of the op amp when there is no feedback is the open loop gain, and the gain when feedback is considered is closed-loop gain.Q3: If the op amp has ideal AC characteristics, the Bode plot (gain-frequency response) is a unipolar system. What is the gain slip rate in dB / decade?A: In a unipolar system, the gain drops (or decreases) at 20dB / decade, which is 6dB / octave. This is responsive to any single pole, and it is also suitable for a simple RC filter or an ideal operational amplifier. However, because op amps have more high-frequency poles, the phase shift will begin to increase as the frequency approaches the unity gain frequency of the op amp.Q4: What is the difference between unity gain bandwidth, gain bandwidth product (GBP), and -3dB frequency?A: Many op amps have an open-loop gain reduction rate of -20db / decade when the frequency is stable. At any point during this descent phase, the GBW is a constant. If the unity-gain operation of the op amp is stable, then the unity-gain bandwidth, or the frequency at which the open-loop gain is 1, is usually equal to GBP. In addition, GBP is not equal to (usually higher than) the unity gain bandwidth. The -3dB frequency is a measure of the bandwidth of an operational amplifier when it is operating in a closed loop. The -3dB point is the frequency at which the gain of the overall closed-loop system drops by 3dB. The unity gain frequency for closed loop applications can be calculated using BW=GBP/Av. The -3dB frequency and unity-gain bandwidth applied depend on the feedback gain setting, output swing, load, and circuit layout.Q5: Why do some amplifiers oscillate with a capacitive load?A: The output impedance of the op amp and the capacitance of the capacitive load may form a resistance-capacitance oscillation. Also they form an R-C oscillation at the output stage, which causes additional phase lag in the feedback signal. CMOS amplifiers have a high output impedance which will cause the electrodes to be approached or lower the unity gain frequency of the op amp. The additional phase lag of the electrodes will weaken the phase margin of the op amp The total phase lag of the amplifier causes the phase angle of the unity gain frequency to increase by more than 180 degrees to cause the total feedback phase shift in unity gain to exceed 180. degree. In addition, the output impedance of a CMOS amplifier is between 100 and 500, causing a relatively low pole frequency. And meanwhile, the output impedance of the high-speed bipolar operational amplifier is in the range of 1 to 100, which causes the pole frequency to be much higher than that of the CMOS operational amplifier, so that the pole is far from the unity gain frequency of the device. The drive of a CMOS amplifier to a capacitive load can be improved by placing an output resistor at the output and an external positive feedback capacitor.Q6: If the output of the op amp stays close to the voltage rail, that is, the output rail, what is the reason?A: There are many ways for operational amplifiers to “rail”. The difficulty is keeping it away from the "rail". If the input exceeds the input voltage range, the output is usually near to a supply voltage rail. In theory, if the output exceeds the actual supply voltage, and a higher supply voltage is given, the op amp will go to rail output again. If there is no feedback or the polarity of the feedback is wrong, the op amp goes to rail output again. At the same time, if the non-inverting input is higher than the negative inverting input, the op amp also goes to rail output. The application of the operational amplifier should be analyzed to ensure that the power supply voltage used has a proper input and gain, so that in normal operation, its input voltage is within the rated value and the output voltage is within the normal range.Q7: What is the difference between the common-mode voltage and input voltage range of an op amp?A: Common mode voltage means that one voltage is applied to both inputs at the same time. Input voltage range is the range of voltages that can be accepted by the input pins. It is necessary to remember that the op amp should suppress the common-mode voltage, and amplify the difference between the two input pins only.Q8: The SPICE model of the bipolar operational amplifier works well, but the SPICE model of the CMOS operational amplifier does not work. Is there a need to set SPICE?A: To input the appropriate bias current to the model, the SPICE model applied on CMOS operational amplifier needs to set the default GMIN option to the largest SPICE package value.Q9: What is the difference between the amplifier's output current and short-circuit current?A: Short circuit current refers to the current generated by the device if the output is connected directly to the power line. This indicates that the output current is limited depending on the design of the device. However, the short-circuit current does not represent the true output of the drive capability of the output. Due to the impedance characteristics of the output stage, the maximum output current is determined by the swing of the output voltage under load. In facet, the smaller the load, the larger the output swing; the larger the load, the smaller the output swing.Q10: How to check the stability of an op amp circuit?A: Check the stability of the control loop, such as the pulse load and related changes in output voltage. The pulse load may be a load current with a pulse or step change, so that the output of the op amp circuit should be connected to a series R-C circuit. The greater the circuit swing or vibration, the worse the stability of the circuit.Q11: Are there any good ways to minimize noise when amplifying a low-level DC signal?A: To obtain a high signal-to-noise ratio, the circuit must be well designed. This includes choosing the best amplifier bandwidth and knowing the impedance of the input signal. If the input signal source has a fairly high impedance, it makes no sense to choose a low voltage noise amplifier, which has high current noise.Q12: How should design a low frequency (<1Hz) differentiator to minimize the output noise?A: The only reason that the output of the differentiator contains noise is because there is a lot of gain and the input is noisy. The traditional differentiator uses Rs-Cs in series at the input and the Rf-Cf in parallel near the operational amplifier. It is not necessary to try more Rs or Cf to minimize noise. The noise of the output come from the differentiator does not mean that it is harmful, because it also amplifies useful signals. In addition, if disconnect a loop, the differential output noise may be beneficial and will stabilize the loop. If the output of the differentiator is quite noisy or has too much input noise, analyze which are the real sources of them.Q13: How to protect the amplifier input from being higher or lower than the supply voltage?A: What must be done is either to clamp the input of the device, or to limit the input current of the device, or ideally, do both. The easiest way is to choose a current limiting resistor to limit this current. The selection is based on the fact that the current generated by the circuit input at the maximum input voltage is less than the maximum current rating of the input pin. Usually, a 1K to 100K resistor in series with this input pin is effective. However, since the signal is usually connected directly to a non-inverting input pin, a non-inverting amplifier may need a protective resistor connected to this pin. For high impedance circuits, a large resistor and or low leakage current diode can be used.Q14: What is the difference between a single-supply amplifier and a dual-supply amplifier?A: There is no difference in the actual circuit, layout, and characteristics of the amplifier. When an operational amplifier is designated as dual power supply, the output load is usually referenced to ground (GND), while a single power supply operational amplifier is usually referenced to the midpoint voltage of a single supply, and it is usually specified to operate on lower voltages, but this is not a necessary requirement. Therefore, whether the op amp is powered by a single 5V power supply and ground (GND), or powered by +2.5 and -2.5V, these is no different. Ⅳ Application: LM358 Classic CircuitsThis Video is Going to Show Top 5 Electronics Project Using OP-AMP LM358The LM358 includes two independent, high-gain, internal frequency-compensated dual operational amplifiers. It is suitable for single-supply operation with a wide range of power supply voltages. It is also suitable for dual-supply operation. LM358 applications include sensor amplifiers, DC gain modules and all other operational amplifiers that can be powered by a single power supply. The classic circuits of LM358 are as shown as following:Figure 1. Active DC-coupled Low Pass RC Filter Figure 2. LED Driver Figure 3. Transistor-Transistor-Logic (TTL) Drive Circuit Figure 4. Active RC Band Pass Filter Figure 5. Squareware Oscillator Figure 6. Hysteresis ComparatorFigure 7. Active Band Pass filter Figure 8. Lamp Driver Figure 9. Current Monitor Figure 10. Low Drift Peak Detector Figure 11. Voltage Follower Figure 12. Power Amplifier Peripheral CircuitFigure 13. Voltage Controlled Oscillator VCOFigure 14. Fixed Current Source Figure 15. Pulse Generator Figure 16. AC Coupled Non-inverting Amplifier Figure 17. AC Coupled Inverting Amplifier Figure 18. Adjustable Gain Instrumentation Amplifier Figure 19. DC Amplifier Figure 20. Pulse Generator Figure 21. Bridge Current Amplifier Figure 22. Introducing Differential Input Signal Figure 23. DC Differential Amplifier Frequently Asked Questions about Op Amps Basics1. What is an op amp basics for dummies?An op amp is a super-sensitive electronic amplifier circuit that's designed to amplify the difference of two input voltages. Thus, an op amp has two inputs and one output. ... Most op amps require both a positive and a negative voltage power supply, with voltages usually ranging from 6 V to 18 V. 2. What is the basic use of op amp?An operational amplifier is an integrated circuit that can amplify weak electric signals. An operational amplifier has two input pins and one output pin. Its basic role is to amplify and output the voltage difference between the two input pins. 3. What is operational amplifier and its types?An operational amplifier (op amp) is an analog circuit block that takes a differential voltage input and produces a single-ended voltage output. Op amps usually have three terminals: two high-impedance inputs and a low-impedance output port. 4. Which purpose the op amp is used?As the name suggests, the purpose of an amplifier or an op amp is to amplify or increase the input signal to produce an output signal which is much larger than that of the input, with a similar waveform as that of the input. The main change in the output signal will be the increase in the power level. 5. What does it mean when an op amp saturates?Originally Answered: What happens when an op-amp is saturated? that means the amplification or gain is so high as to make the output signal with a given input signal, so large as to exceed the compliance range of the power supply of the ope amp. More simply put, if you have an op amp supplied with +/-15V supply rails.

Ⅰ IntroductionWith the improvement of computer technology, the demand for non-volatile memory is increasing, their read and write speed requirements are getting faster and faster, and the power consumption  are becoming smaller and smaller as required by users. But the traditional non-volatile memory such as EEPROM , FLASH, etc. have been difficult to meet these needs.Traditional mainstream semiconductor memories can be divided into two categories: volatile and nonvolatile. Volatile memory includes static random access memory (SRAM) and dynamic random access memory (DRAM). Both SRAM and DRAM lose their saved data when power off. Although RAM is easy to use and performs well, a big disadvantage of it is data loss.Non-volatile memory does not lose stored data in the case of a power failure, because all mainstream non-volatile memories are derived from read-only memory (ROM) technology. ROM, what is called a read-only memory is definitely not easy to write, in fact, it cannot be written at all. All memories developed by ROM technology are difficult to write data, including EPROM, EEPROM and Flash. And these memories not only have a slow writing speed, but also can only be erased and written in a limited number of times.Based on improving semiconductor technologies, ferroelectric memory, a new type of memories, has some unique characteristics. Ferroelectric memory is compatible with all the functions of RAM, and it is a non-volatile memory like a ROM. In other words, ferroelectric memory bridges the gap between these two types of storage, a type of non-volatile RAM. Compared with traditional non-volatile memory, it has attracted much attention due to its advantages such as low power consumption, fast read and write speed, and strong anti-irradiation capability. CatalogⅠ IntroductionⅡ TerminologyⅢ Working PrincipleⅣ FRAM Material FeaturesⅤ Circuit StructureⅥ Reading and Writing ProcessⅦ FRAM StructureⅧ Comparison of FRAM with Other Storage TechnologiesⅨ FRAM UsageⅩ SummaryⅪ One Question Related to FRAM and Going Further11.1 Question11.2 AnswerⅡ TerminologyFerroelectric Memory (FeRAM)Ferroelectric memory (FRAM), also known as F-RAM or FeRAM, is a type of random access memory with fast read and write speed, and the ability to retain data after power is turned off (such as read-only memory and flash memory) is combined, which is the most commonly used type of personal computer memory. Since it is not as dense as dynamic random access memory (DRAM) and static random access memory (SRAM), that is, it cannot store as much data as they do in the same space. In other words, it cannot replace DRAM and SRAM technologies. However, because it can store data quickly with very low power conditions, it is widely used in consumer’s small devices, such as personal digital assistants (PDA), mobile phones, power meters, smart cards, and security systems. FRAM’s read and write speed is faster than flash memory. In some applications, it may also replace electrically erasable read-only memory (EEPROM) and static random access memory (SRAM), and will become a key component of future wireless products. Ⅲ Working PrincipleFeRAM or ferroelectric RAM seems to indicate that an iron element exists within the memory this is not actually the case. A ferroelectric is a material containing a crystal that can spontaneously polarize. It has two states that can be reversed by an external electric field. When an electric field is applied to the ferroelectric crystal, the central atom moves in the crystal following the electric field direction. When an atom moving, it passes through an energy barrier, causing charge breakdown. Internal circuits react to the charge breakdown and set the memory. After the electric field is removed, the central atom remains polarization state, which makes the materials non-volatile, so the state of the memory is preserved. Because there is no atomic collision in the entire physical process, the ferroelectric memory has the characteristics of high read and write speed, ultra-low power consumption, and unlimited writes, making it very suitable to act as temporary storage memory in important systems to transfer various data between subsystems, for each subsystem to read and write frequently.Therefore, with an external electric field, the polarization characteristics of ferroelectric materials will change. When this electric field is removed, the data can still be saved. Without an external electric field, there are two stable states of polarization characteristics. Figure 1 is a hysteresis loop of a ferroelectric material capacitor, showing the different polarities of the ferroelectric capacitor under different applied electric fields. Among them, the two most important parameters are the degree of residual polarization Pr, and the coercive field Ec. In the absence of electric field effect, +/- Pr represents two states of “0” and “1”. To obtain these two states, the applied electric field must be greater than +/- Ec, at this time, the required threshold voltage is also determined.Figure 1. Ferroelectric Hysteresis LoopThe industry explores the use of ferroelectric materials for DRAM: using them as dielectric materials in DRAM capacitors. That is, ferroelectrics are used to replace high-K dielectric materials in standard logic devices, and finally non-volatile transistors are formed, which are FeFETs. The two stable polarization states of the ferroelectric gate oxide change the threshold voltage of the transistor, even when the supply voltage is removed. Therefore, the binary state is encoded in the threshold voltage of the transistor. The writing operation of the memory cell can be completed by applying a pulse on the gate of the transistor, which will change the polarization state of the ferroelectric material and affect the threshold voltage. For example, applying a positive pulse will reduce the threshold voltage, making the transistor in the “on” state. Reading is done by measuring the drain current. This memory mode is similar to the operating mode of a NAND flash: electrons are injected and drawn out of the floating gate, which adjusting the threshold voltage of the transistor.In contrast, the leakage current factor of ferroelectric capacitors is not as important as traditional non-volatile memories such as EEPROM and FLASH, because the information storage of FeRAM is realized by polarization, not free electrons. Ⅳ FRAM Material FeaturesIdeal ferroelectric materials need to meet the following characteristics:Small dielectric constantReasonable self-polarization degree (~ 5μC/ cm2)High Curie temperature (outside the storage and operating temperature range of the device)The thickness of ferroelectric materials should be thin (submicron) to make the coercive field EC smaller. Ferroelectric materials should stand a certain breakdown filed strength.Internal switching speed should be fast (nanosecond level)The ability to keep the data and the long-lasting ability will be good.If used by the military, it is also required to be able to resist radiation exposure. Good chemical stabilityGood processing uniformityEasy to integrate into CMOS processNo bad effect on the surrounding circuitsSmall pollution After years of research and development, there are currently two main types of mainstream ferroelectric materials: PZT and SBT.PZT is lead zirconate titanate PbZrxTil-xO3; SBT is strontium bismuth tantalate Sr1-yBi2 + xTa2O9. The structure of these two materials is shown in Figure 2. Figure 2. Schematic Diagram of PZT and SBT Material StructurePZT is the most studied and widely used. Its advantage is that it can be made at lower temperatures by sputtering and MOCVD. It has the advantages of large residual polarization, cheap raw materials, and low crystallization temperature.; its disadvantages are fatigue degradation problems, and lead pollution to the environment. Moreover, the film deposition process of these materials has proved to be very challenging. At the same time, the extremely high dielectric constant (about 300) of these materials is a big obstacle to their integration into transistors.In addition, scientists have discovered the presence of a ferroelectric phase in a less complex material, hafnium oxide (HfO2), which raise a new concept of storage concept. The researchers found that the ferroelectric phase) can be stabilized by doping silicon (Si) into HfO2. Compared with PZT, HfO2 has a lower dielectric constant and can deposit thin films in a conformal manner (ie, the atomic layer deposition (ALD) process). Most importantly, scientists are familiar with HfO2, because it is the HK gate oxide material in the logic device HKMG. By modifying this CMOS-compatible material, logic transistors can become non-volatile FeFET memory transistors.Functional verification of FeFETs has been implemented in a two-dimensional planar architecture. At the same time, the HfO2 conformal deposition process makes 3D stacking possible, for example, depositing ferroelectric materials on vertical “walls’ to stack transistors in a vertical direction.In terms of materials, 3D FeFETs can solve some of the challenges brought by 2D FeFET structures. One challenge is related to the polycrystalline nature of the HfO2. Scaling the thickness of the HfO2 film will significantly reduce the number of grains in this layer. Because not all the crystal grains have the same polarization direction, the reduction of crystal grains will affect the consistency of the transistor’s response to the external electric field, and eventually lead to large differences between the tubes. By 3D stacking, this drawback is overcome in physical filed. That is, HfO2 does not need to be compressed too thinly, thereby reducing tube-to-tube variation.These vertical FeFETs are expected to have more advantages than complex 3D NAND flash memory, including simple process, lower power consumption and faster speed. Compared to 3D NAND flash memory, vertical FeFET can be programmed at a lower voltage, which improves memory reliability and scalability.The biggest advantage of SBT is that it does not have the problem of fatigue degradation, and it does not contain lead, which meets EU environmental standards; however, its disadvantages are that the process temperature is higher, which makes the process integration difficult, and the degree of residual polarization is small. The comparison of the two materials is shown in Table 1.Table 1. Comparison between PZT and SBT  PZTSBTStructureABO3Layered structureDeposition technologySol-gel,MOCVDSol-gel,MOCVDProcess temperature450℃~700℃750℃~850℃Residual polarity3012Fatigue10101010Data hold85℃@10a- At present, from the perspective of environmental protection, PZT has been banned, but from the perspective of performance and process integration of ferroelectric memory and cost, SBT has no advantages compared to PZT. Therefore, the selection of ferroelectric materials is worth discussing. Ⅴ Circuit StructureThe circuit structure of the ferroelectric memory is mainly divided into the following three types: 2 transistors-2 capacitors (2T2C), 1 transistor-2 capacitors (1T2C), 1 transistor-1 capacitor (1T1C), as shown in Figure 3. The 2T2C structure has two opposite capacitors for each bit as a reference to each other, so the reliability is better, but occupies too much space, which is not suitable for high-density applications. The transistor / single capacitor structure can be used like a DRAM to provide a reference for each column of the memory array, compared with the existing 2T2C structure, they effectively reduce the required space of the memory cell by half. This design greatly improves the efficiency of ferroelectric memory and reduces the production cost of ferroelectric memory products. The 1T1C structure has a higher integration density (8F2), but its reliability is poor. And the 1T2C structure is a compromise between these two structures. Figure 3. Three FRAM StructuresAt present, in order to obtain a high-density memory, 1T1C structure is mostly used (as shown in Figure 4). In addition, a chain structure is also adopted, thus Chain FeRAM is made. This structure is similar to the NAND structure. Through this method, a higher storage density than 1T1C can be obtained, but this method will also greatly increase the access time. Chain FeRAM (CFeRAM) structure is shown in Figure 5. Figure 4. 1T1C Layout Figure 5. Chain FeRAM (CFeRAM) Circuit StructureⅥ Reading and Writing ProcessAccording to the polarity of the electronic memory cell, a small charge amount is “0” and a large charge amount is “1”. This charge is converted into a reading voltage, which is “0” when it is less than the reference voltage and when it is greater than the reference voltage represents “1”. The stored information is read out as shown in Figure 6. Figure 6. Reading and Writing Process of FRAMDuring the reading process, the word line voltage is increased to turn on the MOS transistor, and then the drive line voltage is increased as VCC, so that different charges of the storage capacitor are distributed to the bit line parasitic capacitance, so different voltages appear on the BL to identify the data. During a writing process, the word line is raised to turn on the MOS transistor, and a pulse is applied to the drive line, so that different data on the bit line are stored in two different steady states of the ferroelectric capacitor.By adding a positive voltage or a negative voltage, these two voltages can make the capacitor into two different polarities. In this way, the information is written into the memory. Ⅶ FRAM StructureAt present, the most common device structures of ferroelectric memories are planar and stack structures. The difference between the two is the location of the dry ferroelectric capacitor and the way in which the capacitor is connected to the MOS tube. In the planar structure, the capacitor is placed above the field oxide, and the electrode of the capacitor is connected to the active area of the MOS tube through metal aluminum. The process is relatively simple, but the unit spacing is large. In the stack structure, the capacitor is placed in the source region, the lower electrode of the capacitor is connected to the source terminal of the MOS tube through a plug based on CMP process, which has a high integration density. In addition, the stack structure can adopt the method of making ferroelectric capacitors on metal wires, thereby reducing the mutual influence during the formation process. The following schematic diagrams of the two structures are shown in Figure 7 and Figure 8. Figure 7. Planar Structure Figure 8. Stack StructureThe process of the planar structure is relatively simple. The isolation uses the LOCOS structure, and the planarization does not require the CMP. The stacked structure has a high degree of integration based on advanced technique, and STI is used for isolation, in addition, CMP is required for planarization, and copper wires can be used.In addition, there is a structure that uses a ferroelectric material as the gate. Such a device can eliminate the destructive problem of data readout, and theoretically it is more space-saving and can make more greater integration. However, there are still serious problems with this structure, that is, the data storage capacity is very poor, only one month or less, so it is far from practical. Figure 9 is a schematic diagram of such a structure. Figure 9. FeFET Structure DiagramAt present, the ferroelectric memory generally adopts a planar structure with the line width more than 0.5 μm, and generally uses a stack structure when the line width is less than 0.5 μm. Ⅷ Comparison of FRAM with Other Storage TechnologiesAt present, Ramtron’s FRAM mainly includes two categories: serial FRAM and parallel FRAM. Among them, serial FRAM is divided into I2C two-line FM24×× series and SPI three-line FM25xx series. Serial FRAM is compatible with the traditional 24xx and 25xx E2PROM pins and timing, which can be directly replaced.FRAM products have the advantages of RAM and ROM, and fast read and write speed, in addition, they can be used as non-volatile memory. Due to the shortcoming of ferroelectric crystals, the number of accesses is limited, beyond which FRAM is no longer non-volatile. The maximum access times given is 10 billion, but it not means FRAM will be scrapped when over this upper limit. In the terms of it, FRAM is not non-volatile, but it can still be used as an ordinary RAM.FRAM vs E2PROMFRAM can be used as a second option for E2PROM. Except the performance of E2PROM, the FRAM access speed is much faster. When using FRAM, it must be determined that once there are 10 billion accesses is down to FRAM in the system, there is no damage.FRAM vs SRAMIn terms of speed, price, and convenience, SRAM is better than FRAM; but from the perspective of the entire design, FRAM has certain advantages. Non-volatile FRAM can hold startup programs and configuration information. If the maximum access speed of all the memories in the application is 70ns, one piece of FRAM can be used to complete the system, making the system structure more simpler.FRAM vs DRAMDRAM is suitable for applications where density and price are more important than access speed. For example, DRAM is the best choice for graphics display memory. There are a large number of pixels to be stored, and the recovery time is not very important. If you don’t need to save the last content at the next boot, use volatile DRAM memory. The role and cost of DRAM are reasonable compared with FRAM. In short, it turns out that DRAM cannot be replaced by FRAM totally.FRAM vs FlashAt present, the most commonly used program memory is Flash, which is more convenient and cheaper to use. The program memory must be non-volatile, and easier to rewrite, but the use of FRAM is limited by access times.Ⅸ FRAM UsageData collection and recordingFeRAM allows designers to write data faster and more frequently, and at a lower price than EEPROM.Typical applications: meters (electric meters, gas meters, water meters, flow meters), RF/ID instruments, car black boxes, air bags, GPS, power grid monitoring systems, and so on. Parameter setting and storageFeRAM helps designers solve the problem of data loss due to sudden power failure by storing data in real time. Parameter storage in the FeRAM is used to track the changes of the system in the past time. Its purpose includes restoring the system state or confirming a system error when the power is on.Typical applications: photocopiers, printers, industrial controls, set-top boxes, network equipment  and large household appliances. Non-volatile bufferFeRAM can quickly store data before it is stored in other memory, so that the data in the buffer will not be lost when having power failure.Typical applications: industrial systems, ATM teller machines, tax control machines, commercial settlement systems (POS), fax machines, non-volatile cache memory in hard disk, etc. Ⅹ SummaryFerroelectric memory is an emerging non-volatile memory. It started early and realized industrialization. Because of its advantages such as low power consumption, fast read and write speed, and strong anti-irradiation capabilities, there is a market for small-scale storage areas with low power consumption and radiation resistance. Having the characteristic of anti-radiation, in the case of electromagnetic waves or radiation, the data is still safe, so it has important applications in space science, medicine and other specific fields. However, the ferroelectric memory also has the disadvantages that it is difficult to improve the integration, the process is more contaminated, and it is difficult to be compatible with the CMOS technique. So that it needs further research and solution. Ⅺ One Question Related to FRAM and Going Further11.1 QuestionWhat is FRAM used for?11.2 AnswerFerroelectric RAM is a random-access memory similar in construction to DRAM but using a ferroelectric layer instead of a dielectric layer to achieve non-volatility. It is one of a growing number of alternative non-volatile random-access memory technologies that offer the same functionality as flash memory. FRAM can be used in many fields, for example, with ultra-low power consumption, it is very suitable for intelligent water meters, gas meters and so on. Frequently Asked Questions about Ferroelectric RAM1. What is FRAM memory?Ferroelectric RAM (FeRAM, F-RAM or FRAM) is a random-access memory similar in construction to DRAM but using a ferroelectric layer instead of a dielectric layer to achieve non-volatility. 2. What is ferroelectric effect?Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. ... Thus, the prefix ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. 3. How does FRAM work?FRAM is a nonvolatile storage memory that retains its data even after the power is turned off. However, similar to commonly used DRAM (Dynamic Random Access Memory) found in personal computers, workstations, and non-handheld game-consoles, FRAM requires a memory restore after each read. 4. What are the unique characteristics of FRAM?FRAM has the characteristics of both ROM (Read Only Memory) and RAM (Random Access Memory), and features faster write, great read/write cycle endurance, and low power consumption. 5. Which enables the read and write operation in Feram?Write Operation in Ferroelectric Random Access Memory (FRAM)Similar to read operation, a pre-charge operation follows a write access. The circuit applies 'write' data to the Ferroelectric capacitors. If necessary, the new data simply switches the state of the ferroelectric crystals.

Introduction How to Read an Electrical Diagram Lesson What is a circuit Diagram? Circuit diagram is the basic of engineering research and planning. A schematic layout diagram, which is drawn with the standard symbol of physical electricity, can show the working principle of each component and device relationship, Each electronic component has a symbol. After seeing a few circuit diagrams, you’ll quickly learn how to distinguish the different symbols, and provide planning plan for installing electrons or electrical products. Circuit diagram is one of the basic skills that must be learned by electronic engineers. So this paper gathers the classical circuit materials related to regulated voltage power supply, DCDC conversion power supply, switching power supply, charging circuit, constant current source to provide the most practical circuit diagram reference for engineers. Schematic Symbols Basic Devices   A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.   An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a coil around a core.     An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars.[1] When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode.[2] The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal.       A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal.           Five Parts to Understand Circuit Diagrams *Regulated Power Supply 1. The voltage adjustable range is between 3.5V~25V, the output current is large, using VR- tube circuit to obtain the stable output voltage. Working principle: after rectifying and filtering, DC voltage is supplied by R1 to the base of the adjusting tube, so that the adjusting tube can be switched on. When the voltage passes through the RP, R2 of the V1 conduction, V2 switched on, and then V3 is switched on. At this time, the emitter and collector voltage of V1, V2 and V3 do not change (it acts exactly like a voltage stabilizer). A stable output voltage can be obtained by adjusting RP, and the ratio of R1, PR, R2 to R3 determines the output voltage of the circuit. T: 80W～100W     Input: AC220VOutput Duplex Winding: AC28VRP: 1W (resistance: 250K～330K)FU1: 1A                FU2: 3A~5A VD1 | VD2: 6A02C4: 470µF/35V(electrolytic capacitor)C1: 3300µF / 35VC2 | C3: 0.1µF (MONO CAP)R1: 180～220Ω / 0.1W～1W     Fig 1. VR-tube Circuit 2. Regulated Voltage Adjustable Power Supply Circuit Diagram Whether the computer detection or electronic product can not be separated from the regulated power supply(RPS). This paper introduces one kind of RPS: a DC voltage continuously adjustable from 3V to 15V, the maximum current can be up to 10A, and the circuit uses a high precision standard voltage source integrated circuit (TL431) with temperature compensation which makes the voltage stabilizer more accurate. If there is no special requirement, it can basically meet the normal maintenance. The circuit is shown in the figure below. Fig 2. Regulated Voltage Adjustable Power Supply Circuit Diagram Its working principle is divided into two parts. The first part is a fixed 5V/1.5A power supply circuit; the second part is a high precision and large current regulator circuit which can be adjusted continuously from 3V to 15V. The first circuit is very simple. The DC voltage rectified by silicon bridge QL1 is filtered by C1 from the secondary 8V AC voltage of transformer, then the 5V three-terminal stabilizer block LM7805 can produce a fixed 5V | 1A power supply at the output end without any adjustment. This power supply can be used as an internal power source when the computer board is overhauled. The second part is basically the same as the common series power supply. The circuit is simple, the cost is low, but the voltage stabilizer performance is very high. The resistor R4, the regulator TL431, potentiometer R3 constitutes a continuously adjustable constant voltage source, which provides the reference voltage for the BG2 base. The regulated voltage value of the regulator TL431 is continuously adjustable, which determines the maximum output voltage of the power supply. If you want to expand the range of adjustable voltage, you can change the resistance values of R4 and R3, of course, the secondary voltage of transformer should also be increased. The power of the transformer can be controlled flexibly according to the output current, and the secondary voltage is about 15 V. Bridge rectifier QL, using 15A-20A silicon bridge, compact structure, fixed screws in the middle, can be directly fixed on the shell aluminum plate, better for heat sink. What adjusts the tube is the high current NPN metal shell silicon tube, because it has the very big heat, if the chassis allows, buying the big radiator as far as possible to expand the heat dissipation area; if does not need the big current, a smaller power silicon tube can be used to makes it smaller. The filter uses three 50V/4700uF electrolytic capacitance C5 and C7 in parallel, respectively, to make the output of large current more stable. In addition, this capacitor should be bought with a relatively larger volume, and those smaller ones will also mark 50V/4700uF, but the voltage fluctuates frequently, Or easy to fail for a long time lay idle. Finally, the power transformer can buy a ready-made switching power supply of more than 200W instead of the transformer. In this way, the voltage stability can be further improved, but the manufacturing cost is not too high, and other electronic components have no special requirements. After installation is completed, it can work properly without too much adjustment.   *Switched Power Supply(specific examples) The working principle of integrated control IC-UC3842 for PWM switching power supply The following is the UC3842 internal block diagram and pin diagram. UC3842 uses a fixed frequency pulse width controllable modulation mode, a total of 8 pins, each foot function as follows: Pin① is the output of the error amplifier, and the external resistor-capacitor unit is used to improve the gain and frequency characteristics of the error amplifier; Pin② is the feedback voltage input, which is compared with the 2.5 V reference voltage at the same phase of the error amplifier to generate the error voltage, thus controlling the pulse width; Pin③ is the current detection input, when detecting voltage exceeds 1V, the pulse width is reduced so that the power supply is in the state of intermittent operation; Pin④ is the timing end, the operating frequency of the internal oscillator is determined by the external resistor-capacitor time constant, f=1.8 / (RT×CT); Pin⑤ is the common ground; Pin⑦ is a DC power supply terminal with the function of undervoltage and overvoltage locking, the chip power consumption is 15mW. Pin⑧ is the output terminal of 5V reference voltage, its load capacity is 50mA. Fig 3. IC-UC3842 Electrical Diagram   UC3842 Internal Schematic Diagram UC3842 is an integrated controller of PWM switching power supply with excellent performance, wide application and simple structure. Because it has only one output, it is mainly used for voice control. The UC3842 pin7 is a voltage input with a starting voltage range of 16V-34V. When the power supply is on, the VCC is less than 16V, and the output of the Schmidt comparator is 0. At the same time, no reference voltage is generated and the circuit does not work. When Vcc > 16V, the input voltage Schmidt comparator sends out a high voltage to the 5V fern voltage regulator, which generates a 5V reference voltage. On the one hand, this voltage used in internal circuit; on the other hand, it provides a reference voltage to the outside through pin8. Once the Schmidt comparator flips to a high level (when the chip starts working), Vcc can change in the 10V-34V range without affecting circuit; when the Vcc is below 10V, the Schmidt comparator flips to a low level and the circuit stops working. When the reference voltage stabilizer has a 5V reference voltage output, the reference voltage detection logic comparator outputs a high level signal to the output circuit. At the same time, the oscillator will generate the oscillation signal of the f=Rt/Ct according to the parameters of the pin④ external Rt and Ct, which is added directly to the input of the totem pole circuit, the other is added to the position end of RS flip-flop made by PWM pulse width modulator, and the output end of R connects the output of current-detection comparator. The R-terminal is the control end of the duty ratio. When the R voltage rises, the Q pulse is widened. At the same time, the pulse width of pin⑥ is widened (duty cycle increased); when the R voltage drops, The Q pulse narrows and the pin⑥ pulse width becomes narrow (duty cycle reduced). The sequence of UC3842 points is as shown in the diagram. Only when the E point is in high level, and meanwhile, a point and b point is all in high level, the d point sends out the high level, the c point sends the low level, otherwise the d point sends the low level, c point sends out the high level. Pin② generally connects the feedback signal. When the pin②voltage increases, the pin① voltage will decrease, and the R-terminal voltage will also decrease, so the pin⑥ pulse will narrow, on the contrary, the pin⑥ pulse will become wider. Pin③ is a current sensing terminal. Usually, a small sample resistor is inserted into the source or emitter of the power transistor to convert the current passing through the switch to a voltage, and the voltage is introduced into the pin. When the load short circuit or other reasons cause the current of the power transistor to increase and the voltage on the sampling resistance exceeds 1V, the pulse output pin⑥ is stopped, which can effectively protect the power transistor from damage. Fig 4. UC3842 Internal Schematic Diagram TOP224P 12V | 20W Switching DC Power Supply Circuit Based on Regulated Voltage Two integrated circuits are used in the circuit: TOP224P three-terminal monolithic switching power supply (IC1) and PC817A linear optical coupler (IC2). After UR and Cl rectifier filter, AC power supply produces DC high voltage Ui, to supply primary winding of high frequency transformer T. VDz1 and VD1 can clamp the peak voltage of leakage inductance to the safe value and can attenuate the ringing voltage. VDz1 adopts P6KE200 type transient voltage suppressor with reverse breakdown voltage 200V, and VDl uses UF4005 type UFRD in 1A/600V. The secondary winding voltage is filtered by V, C2, L1 and C3 rectifier, getting 12V output voltage Uo. Uo value is set by the sum of the forward voltage drop UF, R1 of LED and the value of regulated voltage Uz2. Other output voltage values can be obtained by changing the turn ratio of high frequency transformer and the regulated voltage value of VDz2. R2 and VDz2 also provide a false load for 12V output to improve the load adjustment rate at light load. The feedback winding voltage is filtered by VD3 and C4 rectifier to supply the bias voltage required by TOP224P. Since the control current is regulated by R2 and VDz2, the output duty cycle is changed to stabilize the voltage. The common mode choke L2 can reduce the common mode leakage current generated by the waveform of the high voltage switch connected to the D by the primary winding. C7 is a protective capacitor used to filter out interference caused by coupling capacitors of primary and secondary windings. C6 can reduce the differential mode leakage current caused by the fundamental and harmonic waves of the primary winding current. C5 can not only filter the peak current added to the control terminal, but also determine the self-starting frequency, compensating the control loop with R1 and R3. Fig 5. TOP224P 12V | 20W Switching DC Power Supply Circuit The Main Technical Specifications of This Power Supply are as Follows AC Voltage: u=85～265V Voltage Regulation: η=78％ Grid Frequency: fLl=47～440Hz Input Voltage (Io=1.67A): Uo=12V Working Temperature: TA=0～50℃ Maximum Output Current: IOM=1.67A Maximum Output Ripple Voltage: ±60mV Continuous Power Output: Po=20W /TA=25℃ or 15W /TA=50℃）   *DC-DC Power Supply 3V→+5V or +12V Circuit Portable electronic products powered by batteries generally use low power supply voltage, which can reduce the number of batteries and product size. In order to ensure the stability and accuracy of the circuit, it is necessary to use a regulated power supply. If the circuit uses 5V working voltage, but one component requires a higher working voltage, this often makes the designer feeling hard. In this paper, a circuit composed of two booster modules is introduced to solve this problem, and only two batteries are used to supply power. The circuit has fewer components, small size, light weight, stable output of 5V or 12V, and meets the requirements of portable electronic products. +5V power supply can output 60mA, and +12 V power supply maximum output current is 5 mA. Fig 6. 3V→+5V or +12V Circuit The circuit is shown above. It is composed of AH805 and FP106 booster module. AH805 is a kind of boost module with an input of 1.2V~3V and an output of 5V, which can output 100mA current at 3V. FP106 is a chip boost module with input of 4V~6V and output fixed voltage of 29 ±1V, the output current up to 40 mA.  AH805 and FP106 are both a level-controlled to shut down the power. The output voltage of two 1.5V alkaline batteries is 3V, inputting to the AH805, and its output voltage is 5V, inputting 5V to the FP106, and the output voltage is 28V~30V, and then the output voltage is 12 V after through the voltage stabilizer. It can be seen from the diagram that different output voltages can be obtained by changing the stabilizer voltage. Pin⑤ of FP106 is the closing end of controlling the power supply. When Pin⑤ is added a high level > 2.5V, the power supply is switched on; When adding the low level is less than 0.4V, the power supply is off. It can be controlled by circuit or manually. If it is not necessary, Pin⑤ is connected to Pin⑧. MC34063 3.6V→9V Circuit Working State: No-load: Output 3.65V| 18uA  Load: Output 9.88V | 50.2mA; Input 3.65V | 186.7mA, efficiency 72% Working Principle: When there is no load, the IC has no power on pin⑥ and stops working. The input current is only 18uA with input 3.65V. When there is a load (Q1 has Ieb current), the EC pole of 8550 is switched on and the IC is operating. Whether the IC works is determined by whether there is a load or not, it is quite a battery. Using IC has a high voltage conversion efficiency and output stably. If this circuit adds a point of improvement, for example, when increasing power, it can turn into a power supply from 4.2V to 5V without switch. You can use a battery box as a backup power source for your phone. Fig 7. MC34063 3.6V→9V Circuit   *Charging Circuit lm358 basic Battery Charger Circuit Diagram Fig 8. lm358 basic Battery Charger Circuit Diagram There are two different arguments about whether alkaline batteries can be recharged. Some can be filled; the other say it has a risk of explosion. In fact, alkaline batteries can be rechargeable, generally 30-50 times of its service life. In fact, due to the charging methods, there are two different consequences. First of all, there is no doubt that alkaline batteries can be rechargeable, and in the battery instructions, it is mentioned that alkaline batteries are not rechargeable and that charging can lead to explosions. That's true, but note that the word is "could". Actually, it can be viewed as a manufacturer's self-protection statement of exemption. The key to charging alkaline batteries is temperature. As long as you can charge the battery without high temperature, you can successfully do it. The right charging method requires several points: small current: 50mA  charge 1.7V  discharge 1.3V After some people tried charging practice, they said categorically that they could not recharge. The reason for the problems such as lack of charging, short electricity consumption, leakage, explosion, actually, most are charger problems. If the charging current of the charger is too large, far more than 50 ma, and some fast chargers is above 200ma, the direct result is that the temperature of the battery is very high. If the battery is hot, the batteries will leak, and the serious will explode. Some people use Ni-MH rechargeable battery charger to charge, low grade charger does not automatically stop charging function, after long time charging will lead to overcharge then causing battery leakage and explosion. A better charger has the function of automatic shutdown, but the stop charge voltage is generally set to 1.42 V of the Ni-MH rechargeable battery, while the voltage of the alkaline battery is about 1.7V when it fully charged. As a result, the voltage is too low which causing fake charge. And not to wait until the battery is completely out of power to charge, it will lead to poor lifetime of the battery. It is recommended that the voltage of alkaline battery is not less than 1.3V. Therefore, if you plan to charge the alkaline battery, you must have a qualified charger, charging current around 50mA, and charging cut-off voltage is about 1.7V.   Related Description Alkaline manganese rechargeable battery: based on alkaline zinc manganese battery, it is also called mercury-free alkaline manganese battery because of the use of mercury-free zinc powder and new additives. The battery can be recharged for dozens to hundreds of times without changing the discharge characteristics of the alkaline battery, which is more economical. Alkaline zinc-manganese battery was developed in 1882. It was developed in 1912 and put into production in 1949. It has been found that when KOH electrolyte solution replaces NH4Cl as electrolyte, both the electrolyte and the structure change greatly, its performance improved significantly. Features Open voltage is 1.5V Working temperature is between -20℃ to 60℃, it is suitable in alpine region. The capacity of high current continuous discharge is about 5 times that of acid zinc-manganese battery. 2.75W USB Charger This design adopts Power Integrations's LinkSwitch series product LNK613DG. This design is well suited for mobile phones or similar USB charger applications, including mobile phone battery chargers, USB chargers, or any application with constant voltage or constant current. In the circuit, the diode D1 to D4 rectifies the AC input, and the capacitors C1 and C2 filter the DC. The L1, C1 and C2 form a π type filter to attenuate the differential mode conduction EMI noise. These are connected by E-sheild technology of Power Integrations transformers. This design can easily meet the requirements of EN55022 B-type conduction EMI with sufficient margin, and no Y capacitor is required. Fire proof, fusible, winding resistor RF1 provides fault protection and limits surge current generated during startup. Fig 9. 2.75W USB Charger Circuit Fig 9 shows that U1 is powered by optional offset power, which reduces no-load power to less than 40 mW. The value of by-pass capacitance C4 determines the number of cable voltage drop compensation. The value of 1μF corresponds to the compensation of a 0.3Ω / 24 AWG USB output cable. (10μF capacitance compensates 0.49 Ω / 26 AWG USB output cable.). In the constant voltage stage, the output voltage is regulated by switch control. The output voltage is maintained by skipping the switching cycle. By adjusting the ratio of the prohibition period to maintain voltage regularly. This also optimizes the efficiency of the converter throughout the load range. Under the condition of light load (trickle charge), the current limit will be decreased to reduce the magnetic flux density of the transformer, thus reducing the audio noise and switching loss. With the increase of load current, the current limit will increase, and the skipping period will be reduced continuously. When no longer skipping any switching period (maximum power point), the controller in the LinkSwitch-II switches to constant current mode. When the load current needs to be further increased, the output voltage will decrease, and it reflects in the FB pin voltage. In response to the voltage drop of the FB pin, the switching frequency will decrease linearly to achieve constant current output. The RCD-R clamping circuit is composed of D5, R2, R3 and C3, which is used to limit the leakage voltage spike caused by leakage inductance. Resistance R3 has a relatively large value to avoid drain voltage waveform oscillations caused by leakage inductance, which prevents excessive oscillation during turn-off, thus reducing EMI conduction. Diode D7 rectifies secondary and C7 filters it. C6 and R7 together limit the transient voltage spike on D7 and reduce EMI conduction and radiation. The resistor R8 and Zener diode VR1 form an false output load which ensures that the output voltage is within an acceptable limit and that the battery does not discharge completely when the charger is off. Feedback resistors R5 and R6 set maximum operating frequency and output voltage at constant voltage stage.   *Constant-Current Source 1. Discussion on How to Design Three-wire Constant Current Source Driving Circuit The constant current source drive circuit is responsible for driving the temperature sensor Pt1000, to convert its sensing resistive signal with temperature into measurable voltage signal. In this system, the required constant current source should have good temperature stability, large output resistance, output current less than 0.5mA (upper limit of Pt1000 without self-heating effect), earthing at one end of load, and variable polarity of output current. Because the influence of temperature on the parameters of integrated operational amplifier is less significant than of the transistor or FET, the constant current source composed of integrated operational amplifier has the advantages of better stability and higher constant current performance. Especially in the case where one end of the load needs grounding, it has been widely used. So use the dual operational amplifier constant current source shown in figure 2. Amplifier UA1 is used as adder, UA2 as follower, UA1 and UA2 are gain bipolar operational amplifier OP07,  which having low noise, low misalignment and high open-loop. Fig 10. Three-wire Constant Current Source Driving Circuit Vb and Va are the up and down potential of the reference resistor Rref in figure 2: Va is the output of in-phase adder UA1. When taking the resistor R1= R2 , R3=R4, the output current of the Va=VREFx+Vb. It can be seen that the dual operational amplifier constant-current source has the following remarkable characteristics: Load earthing The output current is bipolar when the operational amplifier is supplied by a dual power source. The constant current can be achieved by changing the input reference VREF or adjusting the reference resistor Rref0. It is easy to obtain stable small current and compensation calibration. Because of the mismatch of the resistor, the voltage at both ends of the reference resistance Rref0 will be affected by the terminal voltage Vb of its driving load. At the same time, as a constant current source, Vb will definitely change with the load, which will affect the stability of the constant current source. Therefore, the four resistors R1, R2, R3, R4 are chosen according to the principle that the mismatch should be as small as possible, in addition, the mismatch direction of each pair of resistors should be consistent. In practice, a large number of precision resistors of the same batch can be screened, and 4 resistors with close resistance values can be selected. 2. High Voltage Constant Current Source Circuit Diagram(switch power model) The instrument needs a constant current source that can generate 1mA current on 0 to 3 megabytes ohmic resistance. A design composed with 12V storage battery and UC3845 has be made: the transformer uses a color TV high voltage packet, in which L1 enamelled wire is wound 24 turns on the core of the original high voltage package; L3 uses a coil of the original high voltage package and L2 with the high voltage part of the high voltage packet; L3 and LM393 constitute a voltage limiting circuit which limits the output voltage too high and adjusts the open-circuit output voltage by adjusting R10. Fig 11. High Voltage Constant Current Source Circuit Diagram(switch power model) You May Also Like Filtering Circuit Tutorial (Schematic Diagrams) Switch Mode Power Supply Circuit Design Tutorial Selection Guidance of Five Main Materials for Flexible Circuit Board Production Recommendation MC34063A SOP8 LM7805A UC3842AD   FAQ 1. What are the basic elements of electronics?When building electronic circuits, you will work with a number of basic electronic components, including resistors, capacitors, diodes, transistors, inductors and integrated circuits.   2. What is the schematic symbol represented in the electrical and electronic diagram?It is also called a schematic symbol. Each component has typical functionality according to its operational characteristics. An electronic circuit or schematic drawing uses a wired path between electronic components to complete the circuit. These components are represented by respective symbols for it.   3. What are the 5 components of electricity?The Basics of Electrical ComponentsResistors. The very first component that you should know about is the resistor.CapacitorsLight Emitting Diode (LED)TransistorsInductorsIntegrated Circuit (IC)   4. What are the types of electronics?Electronics has branches as follows:Digital electronicsAnalogue electronicsMicroelectronicsCircuit designIntegrated circuitsPower electronicsOptoelectronicsSemiconductor devices   5. What are the different schematic symbols?Schematic Symbols:Wires (Connected)Wires (Not Connected)DC Supply VoltageGroundNo Connection (nc)ResistorCapacitor, Polarized (Electrolytic)Light-Emitting Diode (LED)   6. What are the electrical diagrams?Image result for Electrical DiagramElectrical diagrams are drawings which are used to represent electrical circuits, these circuits are represented by using lines, symbols, and number combinations. Electrical diagrams show the wiring between components and the relative position of the components.   7. What are the three types of electrical diagrams?There are three ways to show electrical circuits. They are wiring, schematic, and pictorial diagrams. The two most commonly used are the wiring diagram and the schematic diagram.    8. What are the four types of electrical diagram?Image result for Electrical DiagramSome of these electrical drawings or diagrams have been described below.Block DiagramSchematics Circuit DiagramSingle Line Diagram or One-line DiagramWiring DiagramPictorial DiagramLadder Diagram or Line DiagramLogic DiagramRiser Diagram   9. What are the 2 main types of electricity?Current electricity is a constant flow of electrons. There are two kinds of current electricity: direct current (DC) and alternating current (AC).   10. What are the 2 types of electric circuit?Types of Electric CircuitsThere are two types of circuits found in homes and other common devices; namely series circuits and parallel circuits.   11. What is electrical block diagram?Block Diagram – A block diagram shows the major components of electrical or mechanical interrelations in block, or square or rectangular, form. The lines between the blocks represent the connections between the systems or components.   12. What are the 4 basic components of a circuit?Every electric circuit, regardless of where it is or how large or small it is, has four basic parts: an energy source (AC or DC), a conductor (wire), an electrical load (device), and at least one controller (switch). Visualize what happens when you switch on a room light.   13. What is type of wiring diagram?Schematic Diagrams often called a ladder diagram, is intended to be the simplest form of an electrical circuit. This diagram shows the circuit components on horizontal lines without regard to their physical location. It is used for troubleshooting because it is easy to understand the operation of the circuit.   14. What is the main purpose of electrical diagram?Electrical drawings, sometimes referred to as wiring diagrams, are a type of technical drawing that provide visual representation describing electrical systems or circuits. They are used to explain the design to electricians or other workers who will use them to help install or repair electrical systems.   15. Which software is used for electrical design?Top 8 Software For Electrical EngineersAutoCAD ElectricalPLC ProgrammingSCADA SoftwareAC/DC Drive SoftwareProteus And PspiceOrCADXilinxKeil

The solid-state capacitor is called a solid-state aluminum electrolytic capacitor. The biggest difference between it and ordinary capacitors (i.e. liquid aluminum electrolytic capacitors) lies in the use of different dielectric materials. The dielectric materials of liquid aluminum capacitors are electrolyte, while the dielectric materials of solid capacitors are electroconductive polymer materials.   Electronic Basics #14: Capacitors Catalog I. Solid State Capacitor Introduction II. Solid State Capacitor Advantages III. Solid State Capacitor Types IV. Advantages and Disadvantages of Solid Capacitors FAQ   I. Solid State Capacitor Introduction   In view of the many problems of liquid electrolytic capacitance, the solid aluminum electrolytic capacitor has emerged as the times require. Since the 1990s, solid conducting polymer material has been used as cathode instead of electrolyte for aluminum electrolytic capacitor, which has achieved great development. The conductivity of conductive polymer materials is usually 2 ~ 3 orders of magnitude higher than that of electrolytes.    The application of aluminum electrolytic capacitors can greatly reduce the ESR and improve the features of temperature frequency, what’s more, because of the good processability of polymer materials, it is easy to be packaged. All greatly promote the development of aluminum electrolytic capacitance.   On the market, there are two types of aluminum electrolytic capacitors: organic semiconductor aluminum electrolytic capacitors (OS-CON) and polymer conductor aluminum electrolytic capacitors (PC-AC) (PC-CON).    The structure of an organic semiconductor aluminum electrolytic capacitor is similar to that of a liquid aluminum electrolytic capacitor; both are packaged in straight-pin and vertical configurations.   The difference is the cathode material of solid aluminum polymer electrolytic capacitor using the organic semiconductor extract, which can effectively solve the tough problems of electrolyte evaporation, leakage, flammability, and so on. Also, a solid aluminum polymer patch capacitor is a unique structure formed by combining the characteristics of aluminum electrolytic capacitance and tantalum capacitance.   Like liquid aluminum electrolytic capacitors, solid aluminum polymers are mostly in the form of patches. The film of polymer electrode with high conductivity is deposited on alumina as cathode, carbon, and silver as an extraction electrode, which is similar to the structure of solid tantalum electrolytic capacitance.     II. Solid State Capacitor Advantages   （1）With high stability, the solid aluminum electrolytic capacitor can work stably in a high-temperature environment, and improve the performance of the motherboard directly. At the same time, it is suitable for power filters because of its stable impedance in a wide temperature range, provides a stable and abundant power supply effectively, especially in overclocking.    Solid-state capacitors can work at high temperatures and maintain various electrical properties. The capacitance changes less than 15% in the whole temperature range, which is obviously superior to the liquid electrolytic capacitance. Meanwhile, the capacitance of solid-state electrolytic capacitor is independent of its working voltage, so it can work stably in the environment of voltage fluctuation.   （2）The solid-state aluminum electrolytic capacitor has an extremely long service life (over 50 years). It longer than the liquid aluminum electrolytic capacitance. And it will not be broken down, nor need to worry about liquid electrolyte drying and leakage affecting the stability of the motherboard. Solid-state electrolytes do not expand or even burn as liquid electrolytes do at high temperatures. Even if the temperature of the capacitor exceeds its limit, it just melts, which does not cause the capacitor metal shell to burst, so it is very safe.    The working temperature has a direct effect on the life of electrolytic capacitance. Advantages of its electrolyte make a longer service life than liquid electrolytic capacitor under different temperature conditions.   （3）Low ESR(Equivalent Series Resistance) and high mA rms are important indexes of capacitance. The lower the ESR, the faster the charge and discharge speed of capacitance. It directly affects the decoupling performance of the microprocessor power supply circuit, which is more obvious in high-frequency circuits. Therefore, it can be viewed the biggest difference between solid-state electrolytic capacitance and liquid capacitance.   Solid aluminum electrolytic capacitance with the lower ESR and energy dissipation under high power operation conditions can fully absorb the high amplitude voltage between the power lines in the circuit and prevent its interference to the system. When the CPU changes from a low power state to a full load state, the transient (generally less than 5 milliseconds) power required for this CPU switch comes from the CPU power supply circuit, at this moment, the high peak current can be output instantly by the high-speed charge-discharge characteristic of the solid-state capacitor, which can guarantee sufficient power supply and ensure the CPU to work stably.     III. Solid State Capacitor Types     According to the medium, capacitors can be divided into inorganic dielectric capacitors, organic dielectric capacitors, and electrolytic capacitors three categories.   1. Inorganic dielectric capacitors: including familiar ceramic capacitors and mica capacitors, we will often see ceramic capacitors on the CPU. Ceramic capacitors have excellent comprehensive properties and can be used in GHz-class UHF devices, such as CPU/GPU, thus its price is also very expensive.   2.Organic dielectric capacitors: such as thin-film capacitors, which are often used in loudspeakers with their precision, high temperature, and high-pressure resistance.   3. Electrolytic capacitors: known as aluminum capacitors. The traditional method of classifying electrolytic capacitors is based on anode materials, such as aluminum, tantalum, or niobium. However, this method of judging capacitance performance based on the anode is out of date. At present, the key to determine the performance of electrolytic capacitance lies not in the anode, but in the electrolytic, cathode. According to the classification of cathode materials, electrolytic capacitors can be divided into electrolyte, manganese dioxide, TCNQ organic semiconductors, solid polymer conductors, and so on.      IV. Breif Analysis of Advantages and Disadvantages of Solid Capacitors   The dielectric of liquid electrolytic capacitors is liquid electrolyte: liquid particles are very active at high temperatures and have a low boiling point relative to the internal pressure of the capacitor, making it easily explosible. The solid-state capacitance is made of polymer dielectric: at high temperatures, the particle growth and behavior of solid particles are lower than that of liquid electrolytes, and its boiling point will reach 350 degrees Celsius, making it almost impossible to burst.    The ESR of solid-state capacitance in high-frequency operation is shown to be very weak, and the conductivity is very fine. It has the properties of lowering impedance and producing less heat, which is the most obvious between 100KHz and 10MHz.   Traditional electrolytic capacitance is easily influenced by the operating environment's temperature and humidity, and it is less stable at high and low temperatures. The ESR of the solid capacitance can be as low as 0.0040.005 ohms between minus 55 and 105 degrees Celsius, but the electrolytic capacitance varies with temperature.   In terms of capacitance values, liquid capacitance would be lower than the indicated capacitance value below 20 degrees Celsius, and the lower the temperature, the lower the capacitance value. At minus 20 degrees Celsius, capacitance decreases by around 13%, and at minus 55 degrees Celsius, capacitance decreases by 37%. Since solid capacitance decreases by less than 5% at minus 55 degrees, solid state capacitors are guaranteed not to be harmed by lower temperatures. The low-frequency response of solid-state capacitance is not as good as electrolytic capacitance.     In other words, a motherboard with all-solid-state capacitance is not the most reasonable. Whether solid or electrolytic capacitors, their main function is to filter clutter, so long as the capacity and quality of capacitance can reach certain requirements, it can also ensure a stable operation. Solid-state capacitors at 105C have the same lifetime as electrolytic capacitors for 2000 hours.    When the temperature drops, their lives increase, but the solid-state capacitors increase even more. In general, the operational temperature of the capacitor is 70 degrees or less. In addition, the service life of solid-state capacitance can last 23 years, almost six times than the electrolytic capacitance. Compared with electrolytic capacitors, the capacity of electrolytic capacitors is much larger than that of solid capacitors at the same volume and voltage.     At present, solid capacitors are mostly used in the CPU power supply of computer motherboard, but the capacity redundancy is very little, it is necessary to improve the switching frequency of the part of the CPU power supply. Both solid and electrolytic capacitors will have the problem of capacity attenuation in the process of use. However, although the capacity of the circuit board with solid-state capacitance fluctuates slightly, the power supply will appear ripples, which will cause the CPU to work improperly.     Therefore, the lifetime of the solid-state capacitor is very high theoretically, but not in practice. Maintenance when using solid-state capacitor computer board: the power supply part of the CPU is often connected with multiple capacitors, so the solid-state capacitance will not have deformation, explosive slurry, leakage, etc. There is no way to determine which one is out of order basically. Therefore, in maintenance, one of them is often removed (no matter good or bad), and a large-capacity capacitor can be replaced (often with electrolytic capacitance). This method can usually solve the problem quickly.      In theory, the lifetime of the solid-state capacitor is very long, but there will still be a lot of faults in the process of practical use. At present, it seems that most motherboards with overclocking as the selling point put forward by many manufacturers will use solid-state capacitors. But it is not the capacitance that determines the performance of the CPU. The design of the circuit, the development of BIOS, the quality of the CPU itself, and the heat dissipation measures may determine the success or failure of the CPU.   FAQ   1. What is a solid state capacitor? The full name of a solid capacitor is a conductive polymer aluminum electrolytic capacitor, also called a polymer aluminum capacitor. It is currently the highest level of capacitor products. The dielectric material of the solid capacitor is a functional conductive polymer, which can greatly improve the product.   2. Are Solid Capacitors better? Solid capacitors have a higher tolerance not only for higher temperatures, but they also perform better with higher frequencies and higher current than electrolytic capacitors. ... Because there is less impedance at higher frequencies, solid capacitors are more stable and generate less heat than electrolytic capacitors.   3. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   4. What do you need to know about solid state capacitors? Solid-state capacitors have already gone down the altar. Many common electronic and digital products use these products in large quantities. The solid-state capacitors are similar to the common aluminum electrolytic capacitors, some are replaceable, and there is a solid capacitor, sheet, for Replace the common tantalum capacitor.   5. Which is the best electrolytic capacitor for motherboard? Solid aluminum electrolytic capacitors can directly improve the performance of the motherboard. At the same time, it is suitable for power supply filtering due to its stable impedance over a wide temperature range. It can effectively provide a stable and abundant power supply, which is especially important in overclocking.   6. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   7. What is the average lifespan of a capacitor? Design lifetime at rated temperature. Manufacturers of electrolytic capacitors specify the design lifetime at the maximum rated ambient temperature, usually 105°C. This design lifetime can vary from as little as 1,000 hours to 10,000 hours or more.   8. What metals are capacitors made of? There are three different anode metals in use for electrolytic capacitors: Aluminum electrolytic capacitors use a high-purity etched aluminium foil with aluminium oxide as dielectric. Tantalum electrolytic capacitors use a sintered pellet (“slug”) of high-purity tantalum powder with tantalum pentoxide as dielectric.   9. When should you use a capacitor? Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies.   10. How do I choose the right size capacitor? You mainly need to look at 2 values: the voltage and the capacity -both are written on most capacitors-. For example, if you are going to charge a capacitor with 24V, you need to make sure your capacitor will support that voltage; so you'll need a capacitor for at least 25V (plus error margin).       You May Also Like Operational Amplifier(OP Amp) Tutorial Instructions of Common problems in the Application of Inverter About Operational Amplifier LM358: 24 Classical Circuits DIY Community:  DIY Capacitor Flux Capacitor - Back TO The Future

  Solid-state drive or Solid-state disk, abbreviated as SSD, is a computer storage device made of integrated circuits. You can use non-volatile memory (mainly NAND Flash in flash memory) as a permanent storage device, or use volatile memory (such as DRAM) as a temporary storage device. Solid-state hard drives often use SATA, PCI Express, mSATA, M.2, ZIF, IDE, U.2, CF, CFast... and other interfaces. At present, due to the difference between the price per unit and the maximum storage capacity of the mechanical hard disk, the solid state hard disk cannot completely replace the mechanical hard disk for the time being.   How do SSDs Work? | How does your Smartphone store data?  Catalog I What is Solid State Drive? II SSD Classification 2.1 Solid State Drive based on FLASH   Memory 2.2 Solid State Drive based on DRAM III Development History IV SSD Basic Structure 4.1 Main Control Chip 4.2 Cache Chip 4.3 Flash Memory Chip V Compare with Traditional Hard Disk VI SSD Advantages and Disadvantages 6.1 SSD Advantages 6.2 SSD Disadvantages FAQ I What is Solid State Drive?  Solid State Drive, also called solid state disk or SSD, is a hard disk made from an array of solid-state electronic memory chips, consisting of a control unit and a memory unit (FLASH chips / DRAM chips). The interface specification and definition, function and usage method of solid state disk are identical to those of ordinary hard disk drive, and the product shape and size are also the same as that of ordinary hard disk drive.  The working temperature range of SSD chip is very wide: Commercial product: 0~70℃; Industrial product: -40~85℃. Although the cost of manufacturing an SSD is high, it is still gradually being popularized into the DIY market. Due to the difference between solid state drive technology and traditional hard disk drive technology, there are many new memory manufacturers. Manufacturers only need to buy NAND memory, and then they can manufacture solid state disk with proper control chip. The new generation solid state drive generally uses SATA-2 interface, SATA-3 interface, SAS interface, MSATA interface, PCI-E interface, NGFF interface, CFast interface and SFF-8639 interface. II SSD Classification There are two kinds of storage media in solid state drive, one is FLASH chip and the other is DRAM. 2.1 Solid State Drive based on FLASH Memory Solid state drive based on FLASH memory(IDE FLASH DISK, Serial ATA Flash Disk) is using FLASH chips as its storage media. Its appearance can be made into a variety of forms, such as: Laptop hard drive, Micro hard disk, memory card, USB flash disk and etc. The biggest advantage of this SSD is that it is movable, and the data protection is not controlled by power supply. Also, it can be applied to various environments, but its service life is not too long, so it is suitable for individual users. In a flash-based solid state drive, memory cells are divided into two categories: SLC (Single Layer Cell) and MLC (Multi-level Cell).  Solid state drive based on FLASH memory The characteristics of SLC is its high cost, small volume and high speed. And for MLC, it is with characteristics of large volume, low cost but low speed. Each unit of MLC is 2bit, which is exactly twice as many as SLC. However, due to the large amount of data stored in each MLC storage cell and the relative complexity of the structure, the probability of error will increase, so the error correction must be carried out. This action will cause its performance to lag significantly behind the SLC flash memory with simple structure. In addition, the advantage of flash memory is that the number of duplicates is up to 100000 times, which is 10 times higher than that of MLC flash memory. In order to ensure the lifetime of MLC, the control chip is calibrated and the intelligent wear balance algorithm is used, so that the write times of each memory cell can be divided equally, and the mean time between failures (MTBF) can reach 1 million hours.   2.2 Solid State Drive based on DRAM Solid state drive based on DRAM is using DRAM as the storage medium. However, its application range is currently narrow. It follows the design of traditional hard disk, which can be volume setup and managed by most file system tools of operating system, and provides industrial standard PCI and FC interfaces for connecting hosts or servers. The application can be divided into two kinds: SSD hard disk and SSD hard disk array. It is a kind of high performance memory and has a long service life. The downside of it is its need for independent power supply to protect the data security. Solid state drive based on DRAM III Development History > 1956: IBM invented the world's first hard disk. > 1968: IBM restates the feasibility of Winchester technology, which established the development direction of hard disk. > 1970: StorageTek developed the first solid state hard drive. > 1989: The world's first solid state hard disk occurred. > 2006.03: Samsung took the lead in launching a solid state hard disk laptop with 32GB capacity > 2007.01: SanDisk released an 1.8-inch solid state hard disk with 32GB and 2.5-inch model with 32GB in March. > 2007.06: Toshiba has launched its first solid-state hard disk laptop with 120GB capacity. Intel SSD 520 Series > 2008. 09: The official launch of MemoRight SSD marks the accelerated entry of Chinese enterprises into solid state hard disk industry.  > 2009: With the development of SSD , all the manufacturers crushed into this industry , and the storage virtualization then entered a new stage . > 2010.2: Magnesia released the world's first solid-state disk with SATA 6Gbps interface, which breaking through the speed of SATAII interface reading and writing(300MB/s). > The end of 2010: Renice launched and patented the world's first high-performance mSATA solid state disk. > 2012: Apple uses 512GB solid state hard drives on its laptops. > 2015.08.01: TEKISM introduced the first mobile solid-state hard disk with Type-C interface. The SSD provides the latest Type-C interface and supports double-sided insertion of the USB interface. > 2016.01.01: Chinese storage company TEKISM has released the world's first Type-C fingerprint encrypted SSD. SSD M300   IV SSD Basic Structure The FLASH based SSD is the main category of solid state drives. Its internal structure is very simple. The main body of the solid state hard disk is actually a PCB board, and the most basic accessory on this PCB board is the control chip, cache chip(some low-end disks have no caching chip) and NAND flash that used for data storage. The more common solid state hard drives on the market are: LSISandForce, Indilinx, JMicron, Marvell, Phison, Goldendisk and Samsung. The main control chip is the brain of solid state hard drive. One of its functions is to reasonably allocate the load of data on each flash memory chip, and the other is to transfer the whole data and connect the flash memory chip with the external SATA interface. The ability of different master control is very different in data processing ability, algorithm, flash chip reading and writing control , which will directly lead to a ten times gap of solid state hard disk performance. Different SSD 4.1 Main Control Chip Table 1. Brand, model and product of the main control chip for solid state drive 4.2 Cache Chip   The cache chip is next to the main control chip. Solid state drive and traditional hard disk both require high speed cache chip to assist the main control chip for data processing. It is important to be noted here that there are some cheap solid state drive solutions to save the cost of the cache chip, which will have a certain impact on the performance in use.   4.3 Flash Memory Chip Apart from main control chip and caching chip, chips on the other place on PCB board are mainly NAND Flash chips. NAND Flash memory chips are divided into SLC, MLC and TLC NAND Flash memory.    V Compare with Traditional Hard Disk The interface specification and definition, function and usage method of solid state drives are almost the same as those of ordinary hard disk, and the shape and size of solid state drives are basically the same as that of ordinary 2.5 inch hard disk. Solid state drive has the advantages of fast reading and writing, light mass, low power consumption and small volume, which is not possessed by traditional mechanical hard disk. At the same time, its disadvantage is obvious. Although IDC believes that SSD is in the mainstream of the storage market, its price is still relatively high and its capacity is relatively low, once the hardware is damaged, the data is difficult to recover, and others think that the durability of solid state drives is relatively short. The main factors that influence the performance of solid state drive are main control chip, NAND flash media and firmware. Under the same conditions, what kind of interface is adopted may also affect the performance of SSD. The mainstream interface is SATA (including two kinds of interfaces for 3Gb/s and 6Gb/s) and the SSD of the PCIe 3.0 interface. Duo to the difference of the design and the principle of data reading and writing between SSD and the common disk, the internal structure of SSD is also very different. In general, the structure of solid state disk (SSD) is relatively simple and can be disassembled; therefore, most of the articles we see about SSD performance evaluation include an internal disassembly diagram of SSD. On the other hand, the data reading and writing of the ordinary mechanical disk is to lift the magnetic head by the air produced by the high speed rotation of the disc, which makes the magnetic head infinitely close to the disk without contact, and the stepper motor is used to push the head to read the data of changing the track. Therefore, its internal structure is relatively complex, more sophisticated, which is generally not allowed to disassemble. Once human disassembly, there is a strong risk of damage on the disk and disk can not work properly.This is why disassembly diagrams are largely invisible when evaluating ordinary disks.   VI SSD Advantages and Disadvantages 6.1 SSD Advantages   6.1.1 Fast reading and writing Using flash memory as storage medium, the read speed of SSD is faster than mechanical hard disk. SSD does not use (magnetic) head, and its seek time is almost 0. The speed of continuous writing is amazing, and most SSD manufacturers will claim that their solid state drives continue to read and write faster than 500MB / s! The speed of solid state hard disk is not only reflected in continuous reading and writing, but also in random reading and writing speed, which is directly reflected in most of the daily operation. Associated with this are extremely low access times, with the most common 7200 rotary mechanical drives running at 12-14 milliseconds, while solid state drives can easily reach 0.1 milliseconds or less.    6.1.2 Shock resistance Traditional hard drives are disk-type, data is stored in the disk sector. The solid state drive is made from flash memory particles (mp3, U disk, etc.), so there are no mechanical components inside the SSD. This will not affect its normal use even when moving at high speed or even with tilting, and minimize the possibility of data loss in the event of collisions and oscillations. Compared with the traditional hard disk, solid state drive has an absolute advantage.   6.1.3 Low power consumption  The power consumption of solid state drive is lower than that of traditional hard disk.   6.1.4 Noiseless Solid state drive has no mechanical motors and fans inside, thus it works with a noise value of 0 dB.Flash based solid state drives have lower energy consumption and lower calorific emissions (but the consumption of high-end or large-capacity products will be larger). There are no mechanical parts inside, so there will be no mechanical failure, no collision, no shock or vibration. Because the solid state hard disk uses the flash memory chip without mechanical parts, it has the characteristics of low heat emission and fast heat dissipation.   6.1.5 Wide range of working temperature A typical hard disk drive can only work in the range of 5 to 55℃ and most solid state drives can work at -10~70℃. The solid state hard disk is smaller in size and lighter in weight than the mechanical disk of the same capacity. The interface specification and definition, function and usage method of solid state drives are the same as those of ordinary hard disk, and the product shape and size are the same as that of ordinary hard disk. The working temperature range of the chip is very wide(-40~85 ℃).   6.1.6 Lightweight Solid state drives are lighter in weight, 20-30 grams lighter than regular 1.8-inch hard disks.   6.2 SSD Disadvantages  6.2.1 Capacity The maximum capacity of solid state drive is only 4TB. It is SanDisk Optimus MAX   6.2.2 Limited Service Life Solid state drive flash memory has the problem of limitation of erasing times.  A flash memory is completely erased once called a P / E, so the life of flash memory takes P/E units. The lifetime of the 34nm flash chip is about 5000 P / E, while the lifetime of the 25nm is about 3000 P / E. With the improvement of SSD firmware algorithm, the new SSD can provide less unnecessary writing. An 120GB solid state drive that writes 120GB of files to one P / E. In practical use, individual users often write in random rather than continuously. So there will be higher probability of bad sectors. In addition, while each sector of the solid state drive can be repeatedly erased 100000 times(SLC), in some applications such as LOG records in operating system , A sector may be read and written over and over again, in which case the actual lifetime of a solid state disk is not yet tested. However, with the equalization algorithm, the life expectancy of the memory unit is increased by 100000 writes, and the low cost MLCs have only 10, 000 write lives, while the cheap TLC flash memory is only 500 to 1, 000 times.   6.2.3 Expensive The price of the 128GB solid state drive on the market is around RMB550, while the price of the 256GB is around RMB950 .   FAQ   1. Is SSD better than HDD? SSDs in general are more reliable than HDDs, which again is a function of having no moving parts. ... SSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs.   2. What is a solid state drive used for? A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage.   3. Is a 256GB SSD better than a 1TB hard drive? A 1TB hard drive stores eight times as much as a 128GB SSD, and four times as much as a 256GB SSD. The bigger question is how much you really need. In fact, other developments have helped to compensate for the lower capacities of SSDs.   4. Do I need HDD if I have SSD? You don't need both but having a SSD for your operating system and a HDD for your storage drive might be the best bang for your buck. Otherwise, you only need one; a HDD is cheaper, larger, slower, and more prone to data loss. A SSD are normally smaller in storage for the same price but faster and shock resistant.   5. Should I upgrade to SSD? It's time to upgrade to an SSD if you're still using a mechanical hard drive in your computer. ... Solid-state drives are so much faster because they don't have a spinning magnetic platter and moving head. After upgrading, you'll be amazed at the performance improvements and wondering why you waited so long.   6. What are the pros and cons of a solid state drive? a. SSD is faster. b. SSD can take a licking c. HDD is cheaper; SSD is still expensive. d. HDD has greater storage capacity than SSD   7. Do solid state drives crash? SSDs can fail, but in a different way than traditional HDDs. While the latter often fail because of mechanical issues, SSDs may fail due to the methods used to write information. ... Each P/E cycle gradually degrades the memory of an SSD's cells until they eventually become worn down.   8. Can I put SSD and HDD together? The answer is absolutely yes. You can install both, but, SSD will have faster SSD speeds and HDD will still have slower HDD speeds. It is an excellent idea to use SSD and HDD at the same time. An SSD boasts many distinctive merits such as fast loading speed, low power consumption, and etc.     9. How much faster is a SSD than a HDD? As noted above,solid-state drives can read/write speeds of around 550 MB/s faster than a hard disk drive. SSDs can go even faster, provided your computer can handle it. A PCIe SSD can achieve anywhere from 1.2 GB/s to 2.2 GB/s - assuming you have a motherboard that can handle these speeds.   10. How can I tell if my SSD is failing? So here are four signs of SSD failure: Sign #1: Your computer takes a long time to save files. Sign #2: You have to restart often. Sign #3: Your computer crashes during boot. Sign #4: You receive a read-only error.

  Light emitting diode (LED) is a light source that meets the requirements of green lighting. LEDs are safe, efficient, environmentally friendly, long-lived, responsive, small in size and robust in construction with many features that are unmatched by ordinary light-emitting devices. Moreover, it is one of the first semiconductor devices and is widely used. Currently, LEDs are widely used as indicators for various electronic products and as light sources for fiber optic communication.     How dose a diode work?     Catalog I What is a diode? II How dose a diode work? III What is diode characteristics? IV What are diode parameters? V What are the types of diodes? FAQ   I What is a diode?   Diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.) . It has a unidirectional conductivity, that is, the diode anode and cathode to add a forward voltage, the diode conducts. When the reverse voltage is added to the anode and cathode, the diode cuts off. Therefore, the on and off of the diode is equivalent to the on and off of the switch.   In almost all electronic circuits, semiconductor diodes are used. The use of semiconductor diodes in the circuit can play a role in protecting the circuit, extending the life of the circuit. The development of semiconductor diodes has made integrated circuits more optimized and has played an active role in various fields. Diodes have many roles in integrated circuits and maintain the proper functioning of the integrated circuits.     Diodes were one of the first semiconductor devices to be created, and their applications are very widespread. Especially in a variety of electronic circuits, the use of diodes and resistors, capacitors, inductors and other components to make a reasonable connection to form a circuit of different functions, you can achieve a variety of functions such as rectification of alternating current, detection of modulated signals, limiting and clamping, and voltage regulation of the supply voltage. Whether in common radio circuits or in other household appliances or industrial control circuits, diodes can be found.   A diode is made of a PN junction with corresponding electrode leads and a tube housing package. The diode has two electrodes, the electrode leading from the P area is the positive electrode, also known as the anode; the electrode leading from the N area is the negative electrode, also known as the cathode.       Diode structure         There are many kinds of diodes:  - According to the semiconductor materials used, they can be divided into germanium diodes and silicon diodes.   - According to their different uses, they can be divided into detector diodes, rectifier diodes, zener diodes, switching diodes, etc.   - According to the structure of the tube core, they can be divided into point-contact diodes, surface-contact diodes and planar diodes.     --  The point contact diodes are pressed on the smooth surface of the semiconductor wafer with a thin metal wire. With pulse current, one end of the contact wire is sintered firmly with the wafer to form a "PN junction". Due to point contact, only small currents (no more than a few tens of mA) are allowed, which is suitable for high frequency low current circuits, such as radio detection, etc. The area of "PN junction" of surface contact diode is large, which allows large currents passing through and is mainly used in "rectifying" circuits that convert AC to DC.    --  Planar diode is a kind of special silicon diode. It not only can pass through large current, but also has stable and reliable performance. It is widely used in switching, pulse and high frequency circuits.   II How does a diode work? The crystal diode is a p-n junction formed by p-type semiconductor and n-type semiconductor. It forms a space charge layer on both sides of the interface and has a self-built electric field. When there is no applied voltage, the diffusion current caused by the carrier concentration difference on both sides of the p-n junction is equal to the drift current caused by the self-built electric field, so it is in an electric equilibrium state. When the external positive voltage is biased, the mutual suppression of the external electric field and the self-built electric field results in the increase of the carrier diffusion current, which is shown in the conduction region below. When the external reverse voltage is biased, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current I0 independent of the reverse bias voltage value within a certain reverse voltage range, which is shown in the cut-off region below. When the applied reverse voltage is high enough to a certain extent, the electric field intensity in the space charge layer of p-n junction reaches the critical value to produce the multiplying process of the carriers, resulting in a large number of electron hole pairs and a numerical reverse breakdown current is generated, known as the diode breakdown, which is shown in the breakdown region below. III What is diode characteristics? The most important characteristic of the diode is the unidirectional conductivity. In the circuit, the current can only flow from the positive electrode of the diode, and flows out from the negative electrode . The forward and reverse characteristics of the diode are illustrated by simple experiments.   3.1 Forward characteristics In electronic circuits, if the diode is connected to the high potential terminal and the negative electrode to the low potential terminal, the diode will be switched on. This connection is called forward bias. It must be noted that when the forward voltage applied to both ends of the diode is very small, the diode still cannot be switched on, and the forward current flowing through the diode is very weak. Only when the forward voltage reaches a certain value (about 0.6 V of the silicon tube) can the diode be truly switched on. The voltage at both ends of the diode after conduction is called the forward voltage drop of the diode.   3.2 Reverse characteristic In the electronic circuit, the positive end of the diode is connected to the low potential end, the negative electrode is connected to the high potential terminal, and the diode is in the cutoff state. This mode of connection is called reverse bias. When the diode is in reverse bias, there will still be a weak reverse current flowing through the diode, called leakage current. When the reverse voltage of the diode increases to a certain value, the reverse current will increase sharply, and the diode will lose the single direction conduction characteristic. This state is called the breakdown of diode.   IV What are diode parameters? The technical specifications used to test the performance of diodes are called diode parameters. Here are some of the main parameters in diode testing:   4.1 Rated forward working current (IF) Refers to the maximum forward current that is allowed to pass through the diode when it is in continuous operation over a long period of time. When a larger current passes through the diode, the dice is heated and the temperature rises, and when the temperature exceeds the allowable limit, the dice is overheated and damaged. Therefore, it should not exceed the diode rated forward operating current value when the diode is in use. Eg. The rated forward working current of DFM is 1A   4.2 Forward Voltage(VF) Refers to the voltage at both ends of the diode when the rated forward working current IF is passed through the diode. Eg. The voltage at both ends of the diode is about 0.9V when the forward working current of DFM is 1A.   4.3 Maximum reverse operating voltage (VR) When the reverse voltage at both ends of the diode is raised to a certain value, the diode will be broken down and the unidirectional conductivity will be lost. In order to ensure the safety of operation, the maximum reverse operating voltage is specified. Eg. The maximum reverse operating voltage of DF10M is 1100V and the breakdown voltage is about 1400V   4.4 Reverse current IR Refers to the reverse current that flows through the diode when the maximum reverse operating voltage VR is applied to both ends of the diode. The smaller the reverse current, the better the unidirectional conductivity of the diode will be. Eg. When the reverse voltage of DF10M is 1100V, the VR is about 0.2uA.   4.5 Reverse critical current (IZ) Refers to the reverse current of the diode increases sharply to close to the breakdown phenomenon.   Eg. Set the IZ of DF10M to 0.1 Ma (Ma) 4.6 Reverse critical voltage (VZ) Refers to the reverse voltage of the diode when the reverse current is IZ. If the reverse voltage is greater than this value, the reverse current increases dramatically and the unidirectional conductivity of the diode is destroyed, thus causing reverse breakdown. Eg. The VZ is about 1300V when IZ of DF10M is 0.1mA.   4.7 Reverse recovery time (Trr) When diodes are in low frequency applications, it generally do not need to consider its conduction to the cut-off, or cut-off to the transition time. But if the diode works in a high-speed switching circuit environment, when diode suddenly turns to reverse bias from the forward biased conduction state, it will take a certain time to become a cut-off state, which is called reverse recovery time. But if the diode works in a high-speed switching circuit environment, when diode suddenly turns to reverse bias from the forward biased conduction state, it will take a certain time to become a cut-off state, which is called reverse recovery time. Eg. The maximum Trr of EDF1DM is 50nS.   V What are the types of diodes?   5.1 Light emitting diode Light emitting diode, also called LED, is a semiconductor diode that converts electrical energy into luminous energy. Like ordinary diodes, LEDs are made up of a PN junction and have unidirectional conductivity. When a forward voltage is applied to a light-emitting diode, Holes injected from P region to N region and electrons injected from N region to P region are recombined with N region electrons and P region holes in several microns near PN junction to produce spontaneous emission fluorescence.    The energy states of electrons and holes in different semiconductor materials are different. When electrons and holes are combined, the energy released is different. The more energy is released, the shorter the wavelength of light is. The commonly used diodes are red, green or yellow light.The reverse breakdown voltage of a light-emitting diode is greater than 5 volts. Its forward volt-ampere characteristic curve is so steep that it must be used in series to control the current passing through the diode. The current limiting resistance R can be calculated by the following formula: R=（E－UF）/IF . In this formula, E is the power supply voltage, UF is the forward voltage of LED, IF is the running current of LED.   5.2 Zener diode Zener diode, is also called voltage stabilizing diode. By using the reverse breakdown state of pn junction, the current can be changed in a wide range and the voltage is basically unchanged, thus form a diode which has voltage stabilizing function. This diode is a semiconductor device with high resistance until it reaches the critical reverse breakdown voltage.  The following picture is a typical Zener diode application circuit diagram: At this critical breakdown point, the reverse resistance is reduced to a very small value, where the current increases and the voltage remains constant in this low resistance region, and the Zener diode is divided according to the breakdown voltage, because of this characteristic, The regulator is mainly used as a voltage regulator or voltage reference element. Zener diodes can be connected in series for use at higher voltages, and higher stable voltages can be obtained by serializing them.   5.3 Switching diode  Working principle: The semiconductor diode is equivalent to switch-on when it is turned on (the circuit is turned on), and is equivalent to switch-off when it is turn-off (the circuit is cut off), so the diode can be used as a switch. The common used model is 1N4148. Due to the unidirectional conductivity of semiconductor diodes, the PN junction is on at positive bias, and the resistance is very small at the on-state, which ranges from tens to hundreds of ohs. At reverse bias, it is in a cut-off state, and its resistance is very large. Generally, silicon diodes are above 10 μ Ω and germanium diodes have tens to hundreds of kilos. By using this property, the diode will play the role of controlling the current on or off in the circuit and become an ideal electronic switch.   At high frequency, the barrier capacitance of the diode exhibits extremely low impedance and is parallel to the diode. When the capacitance of the barrier itself reaches a certain level, the switching performance of the diode will be seriously affected. In extreme conditions, the diode will be short-circuited, and the high-frequency current will no longer pass through the diode, but will pass directly through the barrier capacitance, and the diode will fail to work. The barrier capacitance of the switching diode is generally small, which is equivalent to blocking the barrier capacitance path and achieving the effect of maintaining good unidirectional conductivity at high frequency.  Classification: General switching diode, high speed switching diodes, ultra-high speed switching diodes, low-power switching diodes, high reverse voltage switching diodes, silicon voltage switching diodes and so on.   5.4 Variable capacitance diode( Varactor Diodes ) Variable capacitance diode, also known as varactor Diodes, are semiconductors that change the junction capacitance according to the voltage supplied. That is, as variable capacitors, they can be used in resonant circuits such as FM tuners and TV tuners and FM modulation circuits. Working principle: Varactor Diodes is a kind of special diode. When applied forward bias voltage, the depletion region of PN (positive and negative electrode) junction is narrowed and the capacitance becomes larger, which results in diffusive capacitance effect. However, the leakage current will be generated when the forward bias is added, so the reverse bias is supplied in application. In fact, we can think of it as a PN junction. If a reverse voltage V is added to the PN junction (the varactor diode is used in reverse direction), the electrons in the N-type semiconductor are directed to the positive electrode and holes in P-type semiconductor will be led to the negative electrode. Then forms a depletion layer that has neither electrons nor holes, and the width of the depletion layer is set to d, which changes with the reverse voltage V. In this way, when the reverse voltage V increases, the depletion layer d becomes wider and the diode capacitance C decreases (according to C=kS/d), and the reverse voltage decreases, the depletion layer width d becomes narrower and the diode capacity becomes larger. The change of reverse voltage V leads to the change of depletion layer, which changes the junction capacity of the variable capacitance diode. - Application: the varactor diode is a semiconductor device based on the principle of variable capacitance between PN junctions. It is used as a variable capacitor in high frequency tuning and communication circuits. As shown in the following figure, the reverse voltage of the diode is changed by changing the different R2. This will result in a change in the capacitance of the diode, thus changing the resonant frequency in which the varactor diode can pull out the full range of the required capacitance in the parallel resonant band-pass filter.   FAQ   1. What is diode and its symbol? Diode, an electrical component that allows the flow of current in only one direction. In circuit diagrams, a diode is represented by a triangle with a line across one vertex.   2. What is special about a diode? Some semiconductor junctions, composed of special chemical combinations, emit radiant energy within the spectrum of visible light as the electrons change energy levels. Simply put, these junctions glow when forward biased. A diode intentionally designed to glow like a lamp is called a light-emitting diode, or LED.   3. Are diodes AC or DC? It allows current to flow easily in one direction, but severely restricts current from flowing in the opposite direction. Diodes are also known as rectifiers because they change alternating current (ac) into pulsating direct current (dc). Diodes are rated according to their type, voltage, and current capacity.   4. Why do we use zener diode? Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits. The load voltage equals breakdown voltage VZ of the diode. The series resistor limits the current through the diode and drops the excess voltage when the diode is conducting.   5. What is unit of diode? A diode is not a measurable quantity. Hence,it does not have a unit. Generally,for a diode,we measure characteristics like forward voltage drop,reverse voltage drop and reverse breakdown voltage which are usually measured in Volts.   6. Do diodes have resistance? Just like a resistor or any other load in a circuit, a diode offers resistance in a circuit. Unlike resistors, though, diodes are not linear devices. This means that the resistance of diodes does not vary directly and proportional to the amount of voltage and current applied to them.   7. Does diode reduce current? Ideally, diodes will block any and all current flowing the reverse direction, or just act like a short-circuit if current flow is forward. Unfortunately, actual diode behavior isn't quite ideal. Diodes do consume some amount of power when conducting forward current, and they won't block out all reverse current.   8. How are diodes classified? Diodes are classified according to their characteristics and are offered in a number of different types, including rectifiers, switching diodes, Schottky barrier diodes, Zener (constant voltage) diodes, and diodes designed for high-frequency applications.   9. What is the most common diode? The most commonly used signal diode is the 1N4148. This diode has a close brother called 1N914 that can be used in its place if you can't find a 1N4148. This diode has a forward-voltage drop of 0.7 and a peak inverse voltage of 100 V, and can carry a maximum of 200 mA of current.   10. What is the difference between a Zener diode and a Schottky diode? As their switching speed is very high, Schottky diodes recover very fast when the current reverses, resulting in only a very small reverse current overshoot. ... A special type of diode, called the Zener diode, blocks the current through it up to a certain voltage when reverse biased.   11. What is difference between Schottky diode and normal diode? In the normal rectifier grade PN junction diode, the junction is formed between P type semiconductor to N type semiconductor. Whereas in Schottky diode the junction is in between N type semiconductor to Metal plate. The schottky barrier diode has electrons as majority carriers on both sides of the junction.   12. Why it is called diode? A diode is called a diode because it has two distinct electrodes (i.e. terminals), called the anode and the cathode. A diode is electrically asymmetric because current can flow freely from the anode to the cathode, but not in the other direction. In this way, it functions as a one-way valve for current.   13. Is a diode the same as a resistor? Key Difference: A diode is a type of electrical device that allows the current to move through it in only one direction. ... A resistor is an electric component that is used to provide resistance to current in the circuit. They are mostly used to produce heat or light.   14. How much voltage can a diode take? Silicon diodes have a forward voltage of approximately 0.7 volts. Germanium diodes have a forward voltage of approximately 0.3 volts. The maximum reverse-bias voltage that a diode can withstand without “breaking down” is called the Peak Inverse Voltage, or PIV rating.   15. Can a resistor replace a diode? Diodes only conduct in one direction whereas resistors conduct in both directions. Without analyzing the actual circuit the results would be unpredictable but, generally speaking, being that diodes & resistors are designed to do different things, substituting one for the other is something you wouldn't want to do.