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Ⅰ IntroductionAs for operational amplifier applications, in electronic circuit, it is usually combined with a feedback network to form a certain functional module, with a special coupling circuit and feedback. Its output signal can be input signal addition, subtraction or differentiation, integration, etc, which early used in analog computers to do mathematical operations. Now they widely used in the electronics industry, regarded as precision AC and DC amplifiers, active filters, oscillators and voltage comparators.This Video is Introducing Operational Amplifier Applications in the CircuitCatalogⅠ Introduction1.1 Integrated Op AmpⅡ Op-amp ParametersⅢ Application MattersⅣ Classic Amplifier CircuitsⅤ One Question Related Op Amp and Going Further5.1 Question5.2 Answer1.1 Integrated Op Amp1.1.1 Evaluation AnalysisIntegrated operational amplifiers are one of the most widely used devices in analog integrated circuits. In various systems, because of different application requirements, the performance requirements of operational amplifiers are also different.Where there are no special requirements, try to use a universal integrated operational amplifier as much as possible, which can reduce costs and easily replace. When using multiple op amps in a system, use as many op amp integrated circuits as possible. For example, LM324 and LF347 always integrate four op amps together in a circuit.The evaluation of integrated op amps depends on their overall performance. Generally, the merit coefficient K is used to measure the excellent degree of integrated operational amplifiers, which is defined as: where SR is the slew rate and the unit is V / ms. The larger the value, the better the AC characteristics of the operational amplifier; The input bias current of the amplifier is lib, the unit is nA; VOS is the input offset voltage in mV. The smaller the Iib and VOS values, the better the DC characteristics of the op amp. Therefore, for circuits that amplify AC signals such as audio and video, op amps with large SR are better; for circuits that handle weak DC signals, op amps with high accuracy are more suitable (both offset current, offset voltage and temperature drift are relatively small).When selecting an integrated op amp, some factors should be considered in addition to the figure of merit coefficient K. For example, the signal source is a voltage source or a current source; the nature of the load, and whether the output voltage and current of the integrated op amp meet the requirements; operating voltage range, power consumption, and volume of the integrated op amp.Figure 1. Using Operational Amplifier as a Comparator1.1.2 Integrated Op Amp Basics Power supplyThe integrated op amp has two power terminals + VCC and -VEE, with different power supply methods. For different power supply modes, the requirements for input signals are different.1) Dual power supplyOp amps are mostly powered in this way. The positive power (+ E) and negative power (-E) relative to the common terminal (ground) are connected to the + VCC and -VEE pins of the op amp, respectively. In this way, the signal source can be directly connected to the input pin of the op amp, and the amplitude of the output voltage can make the positive and the negative symmetrical.2) Single power supplySingle-supply operation connects the -VEE pin of the op amp to ground. At this time, in order to ensure that the internal unit circuit of the operational amplifier has a suitable static operating point, a DC potential must be added to the input end of the op amp. Zero settingDue to the influence of the input offset voltage and input offset current of the integrated op amp, when the input signal is zero, the output is often not equal to zero. In order to improve the operation accuracy of the circuit, it is required to compensate the error caused by the offset voltage and the offset current. This is the zero setting of the operational amplifier. Commonly used zeroing methods include internal zeroing and external zeroing. For integrated op amps without internal zeroing terminals, external zeroing methods should be used. Self oscillationThe operational amplifier is a high-amplitude multi-stage amplifier. Under the condition of deep negative feedback, it is easy to cause self-excited oscillation. To make the amplifier work stably, a certain frequency compensation network must be added to eliminate the self oscillation. In addition, to prevent low-frequency oscillation or high-frequency oscillation caused by the internal resistance of the power supply, an electrolytic capacitor (10mF) and a high-frequency filter capacitor (0.01 mF ~ 0.1mF) should be connected. Device protectionThere are three aspects to the protection of the integrated op amp safety: power protection, input protection and output protection.1) Power protectionCommon faults of power supply are reverse polarity and voltage jump. For a power supply with poor performance, voltage overshoot often occurs at the moment when the power is turned on and off. Protection measures such as the use of FET current source and voltage regulator clamping protection. The voltage regulator’s voltage value is greater than the normal operating voltage of the integrated op amp and less than the maximum allowable operating voltage of the integrated op amp, and the current of the FET tube should be greater than the normal operating current of integrated op amp.2) Input protectionIf the input differential/common mode voltage of the integrated op amp is too high beyond the limit parameter range of the integrated op amp, it will be damaged.3) Output protectionWhen the integrated op amp is overloaded or the output is shorted, the op amp will be damaged if there is no protection circuit. However, some integrated op amps have internal current limit protection or short circuit protection, and no additional output protection is required to use these devices.Figure 2. An Inverting Op Amp CircuitⅡ Op-amp ParametersTo use the op amp better in the circuit, you must have a certain understanding of its internal parameters. Here are the technical parameters closely related to the op amp: Unity-gain bandwidth Definition: Under the condition that the closed-loop gain of the op amp is 1 time, a constant amplitude sinusoidal small signal is input to the input end of the op amp, and the closed-loop voltage gain measured from the output end of the op amp is reduced by 3dB (or equivalent to 0.707 times of the input signal of the op amp), that is to say, the frequency at which the output signal is reduced by -3dB is unity-gain bandwidth. It is a very important indicator. For a sinusoidal small signal amplification, the unity-gain bandwidth is equal to the product of the input signal frequency and the maximum gain at that frequency. In other words, when you know the frequency and gain of the signal to be processed, the unity-gain bandwidth (gain bandwidth = amplification * signal frequency) can be calculated to select the appropriate op amp. The higher the bandwidth, the higher the frequency of the signal that can be processed, and the better the high frequency characteristics, otherwise the signal will be easily distorted.    For small signals, the unity-gain bandwidth is also called the gain-bandwidth product, which can roughly show the ability of the op amp to process the frequency of the signal. For example, the gain bandwidth of a certain operational amplifier is 1MHz, if the actual closed-loop gain is 100, then the maximum frequency for theoretical processing of small signals is 1MHz / 100 = 10KHz.For the bandwidth of a large signal, that is, the power bandwidth, the influence of the slew rate SR is the major factor, and the unit is V/uS. In this case, the power bandwidth calculated by FPBW = SR / 2πVp-p, that is, the gain bandwidth and power bandwidth must be satisfied at the same time when designing the circuit.For DC signals, bandwidth issues are generally not considered, and accuracy and interference are mainly considered.When the amplification factor of an amplifier is n times, it does not mean that all input signals are amplified n times. When the signal frequency increases, the amplification capability decreases. Open bandwidthThe open-loop bandwidth is defined as: inputting a constant-amplitude sinusoidal small signal to the input of the op amp, the frequency measured at which the open-loop voltage gain decrease 3dB from the output of the op amp to the dc gain of the op amp. This is used for very small signal processing. Slew rate SRWith the op amp connected in a closed loop, a large signal (including a step signal) is input to the input of the op amp, and the output rise rate of the op amp is measured from the output of the op amp called SR. Because the input stage of the op amp is switched during the conversion, the feedback loop of the op amp does not work, that is, the conversion rate is independent of the closed-loop gain. The slew rate is a very important index for large signal processing. For general op amps, the slew rate SR <= 10V / μs, and the slew rate of high speed op amps is SR> 10V / μs. The highest conversion rate SR of current high-speed op amps reaches 6000V / μs. The larger the SR, the better the response of the op amp to the input signal changing at high speed. The larger the signal amplitude, the higher the frequency, and the greater the SR. This is used for op amp selection in large signal processing. Full-power bandwidthAt the rated load, under the condition that the closed-loop gain of the op amp is 1 time, a constant-amplitude sinusoidal large signal is input to the input end of the op amp, so that the output frequency of the op amp reaches the maximum (allowing certain distortion) signal. This frequency is limited by the slew rate SR of the op amp. Approximately, full power bandwidth is calculated by formula SR / 2πVop (Vop is the peak output amplitude of the op amp). It is a very important indicator for op amp selection in large signal processing. Setting timeAt the rated load, under the condition that the closed-loop gain of the op amp is 1 time, the time required to input a step large signal to the input of the op amp to increase the output from 0 to a given value. Because it is a step large signal input, a certain jitter will occur after the output signal reaches a given value. This jitter time is called the stabilization time. At this moment, stabilization time + rise time = settling time. For different output accuracy, there is a big difference in the stabilization time. The higher the accuracy, the longer the stabilization time. Equivalent input noise voltageIt refers to any AC random interference voltage generated at the output of an op amp with good shielding and no signal input. When this noise voltage is converted to the input of the op amp, it is called the input noise voltage of the op amp (sometimes expressed by noise current). For broadband noise, the effective value of the input noise voltage of ordinary op amps is about 10 ~ 20μV. This value often corresponds to a certain frequency band. Output impedanceIt refers to the ratio of the change in voltage to the corresponding change in current when the signal voltage is applied to the output of the op amp working in the linear region. At low frequencies it only refers to the output resistance of the op amp. Common mode input resistenceRefers to the ratio of the change in the input voltage of the common mode to the corresponding change in the input current when the two inputs of the op amp input the same signal. At low frequencies, it behaves as a common mode resistance. Generally, the common mode input impedance of the op amp is much higher than the differential mode input impedance, with a typical value above 108Ω. Common mode rejection ratioSame as the definition in the differential amplifier circuit, it is the ratio of the differential mode voltage gain to the common mode voltage gain, which is usually expressed in decibels. It is a parameter that measures the degree of symmetry of the input stage differential amplifier and the ability of the integrated op amp to suppress common mode interference signals. The larger the value, the better. Power supply rejection ratioThe power supply voltage rejection ratio is defined as the change ratio of the input offset voltage of the op amp with the power supply voltage in the linear region. The power supply voltage rejection ratio reflects the effect of power supply changes on the output of the op amp. At present, the power supply voltage suppression ratio is only about 80dB. Therefore, when used for DC signal or small signal processing for analog amplification, the power supply of the op amp needs to be carefully set. Of course, an op amp with a high common mode rejection ratio can compensate a part of the power supply voltage rejection ratio. In addition, when using dual power supplies, the power supply voltage rejection ratio of the positive and negative power supplies may be different. Differential mode input resistanceRefers to the ratio of the change in voltage at the two input terminals to the corresponding change in current at the input terminals when the op amp is operating in the linear region. The differential mode input impedance includes the input resistance and input capacitance, and refers only to the input resistance at low frequencies. General products specification only give input resistance. The input resistance of the op amp using the bipolar transistor as the input stage is not greater than 10MΩ; the input resistance of the op amp as the input stage of the field effect transistor is generally greater than 109Ω. Input offset voltageWhen the input voltage is zero, the output voltage is divided by the voltage gain, plus the negative sign, which is the offset voltage converted to the input. It is the compensation voltage applied at the input when the output voltage is zero. The input offset voltage actually reflects the circuit symmetry inside the op amp. The better the symmetry, the smaller the input offset voltage. The input offset voltage is a very important indicator of the op amp, especially when it is a precision op amp or used for DC amplification.The input offset voltage has a certain relationship with the manufacturing process. It is between ± 1 and 10 mV when op amps use the bipolar process (that is, the standard silicon process). If the field effect tube is used as the input stage, it will be greater. For precision op amps, it is generally below 1mV. The smaller the input offset voltage, the smaller the intermediate zero offset during DC amplification, and the easier it is to handle. Therefore, it is an extremely important index for precision op amps. Input offset voltage driftWithin the specified operating temperature range, it is the ratio of the change in input offset voltage with temperature to the change in temperature. It is actually a supplement to the input offset voltage, which is convenient for calculating the drift of the amplifier circuit due to temperature changes within a given operating range. It is an important indicator for measuring the temperature effect to the op amp. Under normal circumstances, it is about (10 ~ 30) uV / C (degree Celsius), the high quality can be <0.5uV / C. Input offset currentIt is defined as the difference between the base current of the differential pair of the differential input stage when the output DC voltage of the op amp is zero. Used to characterize the degree of asymmetry of the differential input current. The better the symmetry, the smaller the input offset current. Input offset current is a very important indicator for op amps, especially for precision operational amplifier or DC amplifier. The input offset current is approximately one to one-tenth of the input bias current. It has an important impact on small signal precision amplification or DC amplification, especially when a large resistor is used outside the op amp. The effect of input offset current may exceed the effect of input offset voltage on accuracy. The smaller the input offset current, the smaller the intermediate zero offset during DC amplification, and the easier it is to handle. Therefore, it is an extremely important index for precision op amps. Input offset current temperature driftWithin the specified operating temperature range, the ratio of the amount of change in input offset current with temperature to the amount of temperature change. It refers to the temperature coefficient of within the specified operating range, and is also an important indicator to measure the temperature effect on the op amp. It is usually about (1-50) nA / C, and the high quality is about several pA / C. This value is only given in the precision op amp parameters, and it needs attention when it is used for DC signal processing or small signal processing. Input bias current   It is defined as the average value of the bias currents of the two input terminals when the output DC voltage of the op amp is zero, in other words, it is the average current flowing into the input terminal when the operational amplifier is operating in the linear region. The input bias current has a greater impact on the places where input impedance is required, such as high-impedance signal amplification and integrator circuits. The input bias current has a certain relationship with the manufacturing process. If a field effect tube is used as the input stage, the input bias current generally lower than 1nA. It always used to measure the input current of the differential amplifier pair. Maximum differential mode input voltageIt is a voltage that the two input ends of the op amp can withstand. When it is exceeded, the reverse breakdown of the differential tube will occur. The NPN tube made by the plane process has a value of about 5V, and the Vidmax of the horizontal PNP tube can reach more than 30V. Maximum common mode input voltageIt an allowable range of common mode input voltage under normal operating conditions of the op amp. When the input differential pair saturates, the amplifier loses common mode rejection ability. In the case of interference, it is necessary to pay attention to this problem in the use of the circuit. Output peak to peak voltageWorking in the linear region, under the specified load, when the op amp is powered by the large power supply, it is the maximum voltage amplitude that the op amp can output. Except for low voltage op amps, the output peak-to-peak voltage of general op amps is greater than ± 10V, but less than the power supply voltage. This is due to the design of the output stage. The output stage of modern low-voltage op amps has been specially treated. The output peak-to-peak voltage is close to within 50mV of the power supply voltage, so it is called a full-scale output op amp, also known as a rail-to-raid op amp. It should be noted that the output peak-to-peak voltage of the op amp is related to the load, and the value is different for different loads; the positive and negative output voltage swings of the op amp are not necessarily the same. For practical applications, the closer the output peak-to-peak voltage is to the supply voltage, the easier the power supply design.Figure 3. Input Offset Voltage of an Op-ampⅢ Application Matters1) A single-supply op amp must be DC biased, otherwise it will not work properly. For the virtual ground design, in addition to the DC potential, it is necessary to pay attention to the voltage stabilization (it is best to use the reference voltage chip), and also to ensure low impedance AC decoupling, that is, low-frequency decoupling parallel to at least 10uF and high frequency decoupling under 0.1uF.2) The input of the non-inverting amplifier must be biased to ground as a DC path.3) Ordinary op amps cannot directly drive capacitive loads. If there is need, you must use capacitors for phase compensation or output series resistors and then connect the load.4) For the op amp input of the external interface, a TVS tube must be connected in parallel to the positive and negative input pins to prevent the op amp from reversing the polarity due to the too large input voltage signal, forming a parasitic false signal output.5) For amplifier circuits with a gain of more than 10 times, pay attention to controlling the bandwidth gain of the op amp to prevent the device from self oscillation.6) The output of the power amplifier needs to be protected by switching diodes to the power supply and ground, especially when inductive loads are connected.7) When using multiple op amps to process multiple signals, care must be taken to prevent the instantaneous changes in one of the signals from causing crosstalk to the other signal. Therefore, it is recommended not to use one op amp to process multiple signals.8) Most op amp chips are ESD sensitive devices, so pay more attention when using them.9) The pins of unused op amps (excess channels in multiple op amps) should not be left floating, and  grounded or connected to positive and negative power supplies. It is recommended to connect it as a follower (the output is connected to the reverse input) and the non-inverting input is connected to a potential between the power rails (the ground of the dual power system or any suitable point in the circuit). They can also used as buffer amplifiers and add them to a small impact location in the system.Figure 4. Op Amp 741Ⅳ Classic Amplifier CircuitsFigure 5. Inverting AmplifierFigure 5: The grounded non-inverting terminal of op amp is 0V. The inverting and non-inverting terminals are short-circuit, so the inverting end is also 0V. The input resistance of the inverting input terminal is very high, and it is virtual open. In other words, there is almost no current pass through. Therefore, the current flowing through each component in a series circuit is the same, that is, the current flowing through R1 and R2 are the same.Current flowing through R1: I1 = (Vi-V-)/R1Current flowing through R2: I2 = (V--Vout)/R2V- = V+ = 0, I1 = I2Solve the above algebraic equation to get Vout = (-R2/R1)*Vi, it is the input-output relationship of the inverting amplifier. Figure 6. Non-inverting AmplifierIn Figure 6, Vi and V- are virtual short, where Vi = V-. Because of the virtual open, there is no current flow through at the reverse input terminal, then R1=R2. If the current is I, which is obtained by Ohm's law: I = Vout/(R1+R2);Vi is equal to the partial voltage on R2, that is: Vi = I*R2.Virtual short: Vi = V-, R1=R2Ohm's law: I = Vout/(R1+R2), Vi = I*R2Where Vout=Vi*(R1+R2)/R2, represents the non-inverting amplifier. Figure 7. AdderFigure 7: Knowing from the Kirchhoff's law and virtual open theory, the sum of the current through R2 and R1 is equal to the R3, V- = V+ = 0 (short circuit), so (V1 – V-)/R1 + (V2 – V-)/R2 = (Vout – V-) /R3 can be transferred as V1/R1 + V2/R2= Vout/R3. If R1=R2=R3, then the formula becomes Vout=V1+V2, which is an adder. Figure 8. AdderIn Figure 8, because of the virtual open, no current flows through the non-inverting terminal, where V+ = V-, R1=R2, R4=R3, therefore, (V1 – V+)/R1 = (V+-V2)/R2, (Vout – V-)/R3 = V-/R4 can be simplified as V+ = (V1 + V2)/2 V- = Vout/2. So Vout = V1 + V2 is also an adder. Figure 9. SubtractorFigure 9 shows that the current through R1 is equal to the R2, and R4=R3, therefore, (V2– V+)/R1 = V+/R2, (V1 – V-)/R4 = (V--Vout)/R3. If R1=R2, then V+ = V2/2; if R3=R4, then V- = (Vout + V1)/2, because of V+ = V-, so Vout =V2-V1 is a subtractor. Figure 10. Integrator CircuitIn Figure 10, the input voltage at the inverting terminal is equal to the non-inverting terminal because of short circuit; the current through R1 is equal to the C1 because of virtual open. The current flowing through R1 and C1 are Ri=V1/R1, Ci=C*dUc/dt=-C*dVout/dt, respectively. So Vout=((-1/(R1*C1))∫V1dt, which is a integrator circuit. If V1 is a constant voltage U, then the above formula is transformed to Vout = -U*t/(R1*C1)t, then the Vout is a straight line that changes with time. Figure 11. Differential CircuitIn Figure 11, the current through capacitor C1 and resistor R2 is equal because of virtual open; V+ = V- because of short circuit, where Vout = -i * R2 = -(R2*C1)dV1/dt, which is a differential circuit. If V1 is a DC voltage, the output Vout corresponds to a pulse in the opposite direction to V1. Figure 12. Differential Amplifier CircuitFigure 12:Vx = V1……a, Vy = V2……bthen R1, R2, R3 can be regarded as a series, R1=R2=R3, the current I=(Vx-Vy)/R2……cwhere Vo1-Vo2=I*(R1+R2+R3) = (Vx-Vy)(R1+R2+R3)/R2 ……dIf R6=R7, then Vw = Vo2/2 ......e, similarly, if R4=R5, then Vout – Vu = Vu – Vo1, so Vu = (Vout+Vo1)/2 ……fdue to short circuit, Vu = Vw ……g, based on efg formulas, Vout = Vo2 – Vo1 ……hGet from dh, Vout = (Vy – Vx) (R1+R2+R3)/R2, where (R1+R2+R3)/R2 is a fixed value. This value determines the amplifier multiple of the difference (Vy-Vx), thus it is a differential amplifier circuit. Figure 13. Amplifier CircuitIt is a relatively common amplifier circuit. Many controllers accept 0~20mA or 4~20mA current from various measuring instruments. The circuit converts the current into voltage signal to become a digital signal by ADC. Figure 13 is such a typical circuit. As shown in Figure, 4~20mA current flows through the sampling 100Ω resistor R1, there will be a voltage difference of 0.4~2V on R1. Due to virtual open circuit, R3= R5 and R2=R4.Therefore: (V2-Vy)/R3 = Vy/R5 ……a  (V1-Vx)/R2= (Vx-Vout)/R4 ……bShort circuit: Vx = Vy ……cCurrent changes from 0~20mA, then V1 = V2 + (0.4~2) ……dPut cd formulas into b formula: (V2 +(0.4~2)-Vy)/R2 = (Vy-Vout)/R4 ……eIf R3=R2 , R4=R5, then e-a gets Vout =-(0.4~2)R4/R2 ……fIn Figure 13, R4/R2=22k/10k=2.2, then f formula Vout = -(0.88~4.4)V, that is to say, the current of 4~20mA is converted into a voltage range of -0.88~-4.4V. Current can be converted into voltage, and voltage can also be converted into current. Figure 14 is such a circuit. The negative feedback in the above figure does not directly feedback through the resistor, but the emitter junction of the transistor Q1 is connected in series. But it isn't a comparator. As long as it is an amplifying circuit, the law of short circuit and virtual open still conforms.Figure 14. Amplifier CircuitDue to virtual open, no current flows through the input of the op amp,Then (Vi – V1)/R2 = (V1 – V4)/R6 ……aSimilarly (V3 – V2)/R5 = V2/R4 ……bsince short circuit, V1 = V2 ……cIf R2=R6, R4=R5, then V3-V4=Vi can be obtained from abc.The above formula shows that the voltage across R7 is equal to the input voltage Vi, then the current through R7 is I=Vi/R7. If the load RL<100KΩ, the current through R1 and R7 are basically the same. Ⅴ One Question Related to Op Amp and Going Further5.1 QuestionWhat the Application of an Op Amp as a Phase Shifter?5.2 AnswerIn electronic circuit, op amp is used for direct coupling procedure and so DC voltage level at the emitter terminal increases from phase to phase. This rapidly increasing DC level is likely to shift the operating point of the upcoming stages. Thus to move down the increasing voltage swing, this phase shifter is applied.The phase shifter performs by adding a DC voltage level to the output of fall stage to pass the output to a ground level. Frequently Asked Questions about Operational Amplifier Applications1. Why is it called operational amplifier?It's called an “operational” amplifier because it performs a mathematical operation. The most obvious one is multiplication - it amplifies an input signal by a constant. ... But many different 'operations' can be performed by different circuit topologies. 2. What is inside an operational amplifier?Operations amplifiers — op-amps for short, are integrated circuits, constructed mostly out of transistors and resistors. These integrated circuits multiply an input signal to a larger output. You can use these components with voltage and current in both DC and AC circuits. 3. What are operational amplifiers used for?Op amps are used in a wide variety of applications in electronics. Some of the more common applications are: as a voltage follower, selective inversion circuit, a current-to-voltage converter, active rectifier, integrator, a whole wide variety of filters, and a voltage comparator. 4. What are linear applications of op amp?A linear amplifier like an op amp has many different applications. It has a high open loop gain, high input impedance and low output impedance. It has high common mode rejection ratio. Due to these favourable characteristics, it is used for different application. 5. How does an operational amplifier work?An operational amplifier, or op amp, generally comprises a differential-input stage with high input impedance, an intermediate-gain stage, and a push-pull output stage with a low output impedance (no greater than 100 Ω). ... That is, the output gets fed back to the inverting input through some impedance. 6. What do you mean by differential amplifier?A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs and and one output in which the output is ideally proportional to the difference between the two voltages. 7. What are the non linear applications of op amp?Non-Linear Applications of Op AmpVoltage comparator.Two applications of comparator as window detector and zero crossing detector.Schmitt trigger circuit with the extension of regenerative comparator.Multivibrator circuits.Precision rectifier or super diode with the combination of op amp as voltage follower and a diode. 8. Why do we use differential amplifier?Differential amplifiers are used mainly to suppress noise. ... Noise is generated in the wires and cables, due to electromagnetic induction, etc., and it causes a difference in potential (i.e., noise) between the signal source ground and the circuit ground. 9. What does an operational amplifier do?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. 10. What is an ideal operational amplifier?Operational amplifier: The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.

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. IntroductionIn electronics, an operational amplifier is a circuit unit with a very high amplification factor. In the actual circuit, usually combined with the feedback network to form a certain functional module. It is an electronic device with a special coupling circuit and feedback. The output signal can be the result of mathematical operations such as addition, subtraction or differentiation, integration, etc, thus it was used in analog computers to implement mathematical operations.CatalogⅠ. IntroductionⅡ. Non-inverting Amplifiers and Inverting Amplifiers   2.1 Terminology   2.2 Non-inverting Amplifier Circuit   2.3 Inverting Amplifier CircuitⅢ. Note: Input ImpedanceⅣ. Amplifier GainⅤ. Differences between Inverting & Non-Inverting Amplifiers   5.1 Facts Consideration   5.2 Differences SummaryⅥ One Question Related to Amplifier and Going Further   6.1 Question   6.2 AnswerAn op amp is a functional unit that can be implemented in discrete devices or in semiconductor chips. With the development of semiconductor technology, most of the op amps exist in the form of a single chip, but there are many types of op amps, which are widely used in the electronics industry. The op amp can be simply viewed as a high-gain direct-coupled voltage amplifying unit with one signal output port (Out) and two high-impedance inputs, non-inverting input and inverting input, so op amps can be used to make the non-inverting, inverting, and differential amplifiers.Difference between Inverting and Noninverting Amplifier Ⅱ. Non-inverting Amplifiers and Inverting Amplifiers2.1 TerminologyAn operational amplifier in an electronic circuit has a non-inverting input and an inverting input. The same polarity of the input and the output is a non-inverting amplifier, on the contrary, it is an inverting amplifier. And the inverting amplifier circuit has a function of amplifying the input signal and inverting the output. 2.2 Non-inverting Amplifier CircuitWhen a positive phase is received, a positive phase is output, whereas the negative phase is output. The phases of non-inverting end and the output end are the same. In other words, the signal is applied to the non-inverting input of the op-amp, and it is not inverted at the output when compared to the input. Figure 1. Non-inverting Amplifier(A signal applied keeps its polarity at the output, and a positive input remains a positive output.)Vin and V-Virtual are short circuit in the figure, where Vin=V-……aBecause of the virtual open circuit, there is no current to the inverting input, the current through R1 and R2 is equal, and the current is set to I, which is obtained by Ohm's law:I=Vout/(R1+R2)……bVin equal to the partial voltage on R2, where Vin=I*R2……cBy a, b, c, where Vout=Vin*(R1+R2)/R2 2.3 Inverting Amplifier CircuitWhen the positive phase is received, the negative phase is output, whereas the positive phase is output. And the non-inverting end and the output end are keeping inverting relation. An inverting amplifier provides the same function as the common emitter and common-source amplifier.Figure 2: The grounding of the op amp is 0V, the inverting end and the non-inverting end are short circuit, so it is also 0V. The input resistance of the inverting input is very high, while it is virtual open. So that there is almost no current injection and outflow, then R1 and R2 are equal to a series connection, the current flowing through each of the components in a series circuit is the same, that is, the current flowing through R1 and the current flowing through R2 are the same. Figure 2. Inverting Amplifier(The polarity of a signal is reversed at the output, and a negative input becomes a positive output.)Current flowing through R1: I1=(Vin-V-)/R1………aCurrent flowing through R2: I2=(V--Vout)/R2……bV-=V+=0………………cI1=I2……………………dBy solving the above algebra equation, we can get the result:Vout=(-R2/R1)*ViThe inverting amplifier circuit has the function of amplifying the input signal and inverting output, which is a negative feedback technique. Negative feedback returns a portion of the output signal to the input. The reason why the inverting amplifier can only connect the signal to the inverting input is because the negative feedback can be formed only in this way, otherwise it will not work in the linear amplification region.When inputting from both ends simultaneously, the size and phase are the same, that is the common mode signal, and the theoretical output is zero. Ⅲ. Note:  Input ImpedanceThe input impedance of the non-inverting input is high, and the input impedance of the inverting input is low. The input impedance of the non-inverting input is basically determined by the bias resistor connected in parallel with the non-inverting terminal, and the resistance can be very large. When the inverting input is connected, the feedback resistor is connected between the inverting terminal and the output terminal, and the resistance is small, so the input impedance of the inverting input is relatively low.1. The magnitude of the input resistance of the non-inverting amplifier does not affect the input impedance, and the inverting amplifier input resistance is approximately equal to the input impedance.2. When the input impedance is required to be high, the non-inverting amplifier should be selected.3. If the input impedance is not required to be large, the non-inverting or inverting can be selected at this time. When the phase is not considered strictly, the inverting amplification is preferred because it only has the differential mode signal.4. The CMRR of the inverting amplifier is better when the CMRR is decisive.Inverting amplifier, the input common mode of the op amp is almost constant, the common mode amplification is not reflected to the output, and the input common mode of the op amp in the non-inverting amplifier changes with the input signal, the common mode amplification of the op amp will be reflected Output. Therefore, the CMRR of the inverting amplifier is better when the CMRR of the op amp is decisive. Ⅳ. Amplifier GainBasic Inverting Amplifier Made with an Op-ampNon-inverting AmplifierInverting AmplifierGAIN (AV) = 1+(R2 / R1)Example:if R2 is 1000 kilo-ohm and R1 is 100 kilo-ohm the gain would be :1+ (1000/100) = 1 + 10 or GAIN (AV) = 11If the input voltage is 0.5v the output voltage would be : 0.5 X 11 = 5.5vGAIN (AV) = -R2 / R1Example:if R2 is 100 kilo-ohm and R1 is 10 kilo-ohm the gain would be :-100 / 10 = -10 (Gain AV)If the input voltage is 0.5v the output voltage would be : 0.5v X -10 = -5v Ⅴ. Differences between Inverting & Non-Inverting Amplifiers5.1 Facts ConsiderationIt can be seen that comparing them is from the following aspects: input and output impedance, common mode anti-interference.1. The input impedance of the non-inverting amplifier is equal to the input impedance of the op amp, and they are close to infinity. The input resistance of the non-inverting amplifier does not affect the input impedance; and the input impedance of the inverting amplifier is equal to the resistance of the series resistor of the signal to the input. Therefore, when the input impedance is required to be high, the non-inverting amplifier should be selected.2. The input signal range of the non-inverting amplifier is limited by the op amp's common-mode input voltage range, while it is not the case with the inverting amplifier. Therefore, if the input impedance is required to be low and the phase is free, the inverting amplification is preferred because it only has a differential mode signal. And the anti-interference ability is strong, thus a larger input signal range can be obtained.3. In the design where the same magnification is required, try to select a resistor with a small value, which can reduce the influence of the input bias current and the influence of the distributed capacitance. If you are more concerned about power consumption, you have to compromise on the resistance.4. Determine if an input signal is a non-inverting input or an inverting input. If the input resistance of the amplifier circuit is required to be large, the non-inverting input amplifier circuit should be used because the increase of the input resistance of the amplifier circuit will affect the voltage gain. When the inverting input resistance is increased, the voltage gain of the circuit is reduced, and the voltage gain is also affected by the internal resistance of the signal source. Therefore, when designing the inverting input amplifying circuit, sometimes the input resistance and the voltage gain is difficult to balance. If the bias resistor or the voltage divider is appropriately increased, the input resistance of the amplifier circuit can be increased, and the voltage gain has little or no effect on the voltage gain, which requires a better understanding of the circuit.Figure 3. Integrated Circuit Using Op-amp5.2 Differences SummaryThe integrated amplifier can be connected to the non-inverting or to the inverting amplifier. Is it better to select non-inverting amplification or inverting amplification? Let's look at the difference between them.1）non-inverting amplifiera. AdvantagesThe input impedance is equal to the input impedance of the op amp, which close to infinity.b. DisadvantagesThe amplifying circuit has no virtual ground, so it has a large common mode voltage, and the anti-interference ability is relatively poor. So that the op amp requires a higher common mode rejection ratio, and another disadvantage is that the amplification factor can only be greater than one.2）inverting amplifiera. Advantages The potential of the two input terminals is always approximately zero (the non-inverting terminal is grounded, and the inverting terminal is virtual-grounded), in addition, only the differential mode signal exists, and the device has strong anti-interference ability.b. Disadvantages The input impedance is small, which is equal to the resistance of the series resistance of the signal to the input.3) The gain calculation of the two are different, and their phases are opposite. Ⅵ One Question Related to Amplifier and Going Further6.1 QuestionWhat are non-inverting amplifiers used for?6.2 AnswerThe non-inverting amplifier configuration is one of the most popular and widely used forms of op amp circuit and it is used in many electronic devices. The op amp non-inverting amplifying circuit provides a high input impedance along with all the advantages gained from using an op amp. Frequently Asked Questions about Difference between Inverting and Noninverting Op Amp1. Which is better inverting or noninverting amplifier?Inverting op-amps provide more stability to the system than non-inverting op-amp.In case of inverting op-amp negative feedback is used that is always desirable for a stable system. 2. What are the advantages of non inverting amplifier over inverting amplifier?The advantages of the non-inverting amplifier are as follows: The output signal is obtained without phase inversion. In comparison to the impedance value of the input at the inverting amplifier is high in the non-inverting amplifier. The voltage gain in this amplifier is variable. 3. What is an inverting amplifier used for?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it. 4. Where are non-inverting amplifiers used?The non-inverting amplifier configuration is one of the most popular and widely used forms of operational amplifier circuit and it is used in many electronic devices. The op amp non-inverting amplifier circuit provides a high input impedance along with all the advantages gained from using an operational amplifier. 5. Why are inverting amplifiers better than non inverting?Inverting op-amps provide more stability to the system than non-inverting op-amp.In case of inverting op-amp negative feedback is used that is always desirable for a stable system.

Warm hints: The word in this article is about 3000 words and reading time is about 15 minutesSummaryThis article is mainly about space monitoring and location technology of AR&VR equipment. All AR&VR products must have accurate spatial monitoring and positioning capabilities in order to achieve a full range of head， hand interactions in order to provide users with a more realistic virtual experience. CoreResearch on space monitoring and location technology of AR&VR equipmentPurposeIntroduce space monitoring and location technology of AR&VR equipmentProductAR&VR EquipmentCategoryElectronic productsApplicationsAR&VR technologyTechnologyInside-out space monitoring and positioning and outside-in space monitoring and positioning     Catalogs CatalogsI、Current Status of AR&VR ProductsV、 PC VRII、Cardboard productsVI、Space positioning technology categoryIII、Head motion controlled all-in-one            machine1. Inside-out space monitoring and positioning technologyIV、 AIO machine with space monitoring and positioning2. Outside-in space monitoring and positioning technology  Introduction I、Current Status of AR&VR ProductsThere are many AR&VR products already on the market. The price varies from Cardboards to Hololens, and the user experience varies greatly. First of all, VR products can be divided into the following categories: cardboard products, one-touch control integrated machine, AIO machine with space monitoring and positioning, PC VR.  DetailII、Cardboard productsCardboard productsThis kind of product is the simplest VR product. It comes from Google's carton VR box. Simply, it uses two convex lenses to project the contents of the mobile phone into screens. It uses the IMU inside the phone to judge the user's head movement to adjust the movement direction of the VR display content. This kind of product began to ship a large number of domestic white cards in 2015, but the overall effect of VR depends on the configuration of the mobile phone and the quality of the optical lens. It is only an entry-level VR experience product.The first generation VR products of game companies and some domestic video content are basically in this form. The most representative is the Storm Box, with a BT control handle for menu selection. The emergence of this type of product has indeed played a big role in the promotion of the entire VR industry, but its drawbacks are also very obvious. The Cardboard-style VR device ushered in a particularly big opportunity in 2016, that is, Google proposed Daydream VR. Google wants to enhance the VR Cardboard users’ experience, and hopes to be able to dominate the entire VR ecosystem in 2016. The Daydream mobile phone Pixel, Pixel XL and Daydream Viewer wearing the Cardboard were released in the year, and also equipped with a built-in IMU remote control handle. According to Google's requirements for VR device user experience, it must reach a mobile phone with a certain hardware configuration, and with Daydream Viewer running related VR applications, so that users will not be dizzy. Since 2016, with the launch of products such as Huawei P9 and Lenovo MotoZ, there are more and more mobile phones supporting Daydream. It is expected that, in 2017, these products will completely break the stalemate of the poor Cardboard user experience.III、Head motion controlled all-in-one machineAll-in-one machineAIO machine, as its name, is a VR device that does not need to be inserted into a mobile phone or connected to a PC. Currently, there are representative DaPeng, Xiaoniao, KanKan, etc. Most of the products are listed in 2016. The features of these products are basically the same use of 1080p or 2K resolution display screens (some of which also use 2Kx2 dual screens) with specially designed FIN products designed for VR products aspherical optical lens. The overall picture quality and distortion have improved a lot. However, these products have a common feature, that is, only a simple head control, can only sit or stand in place by shaking his head to achieve VR control, can not do the first hand interaction. In order to remedy this defect, there are currently some external accessories with spatial position detection (the built-in IMU handle, somatosensory backpack, spatial positioning light ball, etc.) to enhance the overall VR user experience.IV、 AIO machine with space monitoring and positioningAIO machine with space monitoring and positioningSpace monitoring and positioning are generally two ways, Inside-out and Outside-in. Inside-out senses the spatial information outside the device through the built-in sensor and performs related positioning. The Outside-in is just the opposite. It uses an external sensor to sense the position of the VR device and provides positioning information to the VR application. For the all-in-one machine, the current view has selected the Inside-out solution without exception, thus avoiding the need to install an external sensor in advance. The user can pick up the VR device at any time and anywhere. It is expected that some of the major products coming on the market in 2017, such as the second generation of the DaPeng AIO Machine and the Storm AIO Machine, will have space positioning capabilities, which will greatly enhance the VR user experience, especially VR games.V、 PC VRPC VRThe most representative products are the HTC Vive, Sony PSVR and HTC Oculus. After the three swordsmen went public in 2016, the HTC Vive has become a standard configuration for the VR experience room. Many other industry customizations are based on Vive. Sony PSVR has sold about 1 million units in less than half a year, which has greatly improved the overall level of user experience in the entire VR industry. The feature of these three products is the use of external space positioning technology. For example, Vive uses an external infrared laser transmitter, head and handle senses transmitter location to determine its position and trajectory. PSVR and Oculus use external sensors to sense the visible light or infrared light emitted by the headlights and the handle to determine the positions of the heads and the handles, so that the heads and the handles can accurately know their respective relative positions and trajectories in space at any time. This can make the application of VR more realistic.Next, let’s talk about AR products. At present, there is a big gap between AR products. Some AR glasses products only project virtual information, images, etc., and are not actually related to the actual environment where the user is located. Such products can only achieve 6DOF motion tracking by the projected virtual information following the head movement. But it is impossible to fuse the virtual object with the actual environment where the user is. For example, the famous ODG, the latest product only supports 6DOF motion tracking, there is no spatial positioning function.AR product ODGShanghai Zhishi's smart glasses also have similar functions to those of ODG, but their positioning is a live broadcast from the first point of view. Therefore, only relevant information and videos for shooting can be displayed in the glasses without spatial positioning. However, it is understood that they are also developing a built-in TOF depth camera glasses, which can achieve 6DOF + spatial positioning function.Shanghai Zhishi's smart glassesThe currently available AR products have the best space monitoring and positioning capabilities. The best match for virtual objects is the Lenovo Phab2 Pro based on Google's Tango space positioning technology and the Microsoft Hololens. Although these two products are very different in shape, they are essentially the full integration of 6DOF+SLAM, achieving spatial positioning and motion tracking. Their AR effects can basically be virtual objects and the actual environment. Convergence, no matter how the user moves or views from what angle, the feeling is just like the real object is in front of me. However, Hololens' accuracy and stability of 6DOF+SLAM are still higher than those of Tango in terms of the effect of actual use. This is closely related to the choice of hardware design platform, type and number of sensors, and core algorithms.Hololens ARIn addition, there are actually many companies in the country that are developing related AR products. Among them, the distinctive feature of Micro Eye's SMAKKEST is not only similar to Hololens, but also similar to Hololens in terms of function. The effect of 6DOF+SLAM is said to be recognized by Hololens.  AnalysisVI、Space positioning technology categorySpace monitoring and positioning technology, in fact, can be divided into two major categories initially, one is the Inside-out space monitoring and positioning, and the other is the Outside-in space monitoring and positioning.1. Inside-out space monitoring and positioning technologyInside-out space monitoring and positioning technology, technology is essentially similar to the process of human-to-environmentally-aware environment of the human eyewear. It senses the external space from the inside of the device and is therefore called the Inside-out positioning method. Inside-out space monitoring and positioning technology is also divided into two categories. One is the spatial monitoring and positioning based on SLAM technology. This is also a basic function required by the fiery robotics industry. SLAM is the English abbreviation for simultaneous localizatiion and mapping. It means that the device itself starts to move from an unknown location in an unknown environment, locates itself according to location estimates and maps during the movement, and builds incremental maps based on its own positioning to achieve autonomous detection and positioning navigation of the device itself. . At present, most AR products use Inside-out spatial location technology.The representative products of the space monitoring and positioning technology based on SLAM are Lenovo Phab2 Pro Tango mobile phone and Hololens. Both use depth monitoring + Fisheye and IMU fusion for sports monitoring. The difference is that the depth monitoring technology is different (Tango uses TOF, and Hololens uses structured light) and the number of Fisheye motion and feature point monitoring is different. Hololens' spatial positioning effect is more accurate and stable than Tango's, and Hololens' effect is in low light and glass light transmission. The current Tango victory, but Tango technology is not static, the next generation of Tango technology also supports multiple Fisheye camera.The Lenovo Phab2 Pro Tango phone uses a TOF depth camera, a 155-degree FOV Fisheye motion monitoring camera and an RGB camera, Fisheye motion monitoring camera with IMU data fusion, feature point matching, providing the device with a complete trajectory The monitoring, together with the cloud image information of the TOF depth camera, can plot the position of the device itself in space and the trajectory of the movement in real time. At the same time, through Tango's own zone learning function, when returning to the space that has already passed, once the Fisheye camera By detecting the stored feature points and matching them, it is possible to quickly perform spatial positioning. This is very important for AR equipment and it ensures that users can quickly use it anytime, anywhere. The working principle of Tango is not explained here. You can refer to Lin Shigong's another article for detailed understanding.The working principle of TangoThe Hololens design of Microsoft is very unique and very affluent. It has newly developed an HPU (Holographic Processing Unit) based on Intel's CPU and GPU technology. The device adopts the configuration of CPU+GPU+HPU. Like Tango, it does not need to External PCs look to achieve complete space monitoring and positioning. On the sensor side, depth monitoring uses two structured light cameras with four structured light-grating emitters for depth monitoring. In addition, there are two Fisheye cameras on the left and right of Hololens, so that more feature points in the space environment can be monitored. Hololens' space positioning accuracy and stability are therefore much higher than those of Tango.HPU（Holographic Processing Unit）The other type is based on the marker (pointer) space monitoring and positioning technology, simply put some like two-dimensional code, special color graphics patterns or light spots as markers in the actual space, equipment to monitor these markers The location of the point to determine their position and movement trends. The HTC Vive is a representative of this type. The following figure shows the working principle of spatial location of the HTC Vive.The working principle of spatial location of the HTC ViveVive emits laser light through two fixed laser emitters. Each base station has an infrared LED array. Two infrared laser emitters with rotating shafts perpendicular to each other are distributed. One is X-axis scanning, and the other is Y-axis scanning. The lasers have a fixed phase difference of 180 degrees. When one of the lasers emits an X-axis scan, the other laser emits a Y-axis scan.The HTC Vive has a shell that is densely covered with 32 light sensors, each oriented in different directions. These sensors are used to receive the infrared laser emitted by a fixed laser emitter. The computer connected to Vive controls all the devices to operate synchronously. The light sensor on the head reveals the time when the laser light reaches each sensor in the X-axis and Y-axis directions and the phase relationship between the two different laser emitters, and the phase difference of each light sensor can be calculated. Accurately locate the head position and trajectory.There are 24 light sensor on the Vive handle. The working principle and head of the handle are the same. It will not be repeated here.The HTC Vive ShellIn addition, it is necessary to mention that domestic Ximmerse, they also introduced a VR device for the Outside-in space positioning package design, through this space positioning package, can provide space-free VR devices with similar accuracy with the HTC Vive Space monitoring and positioning capabilities. The positioning package includes a dual camera module, two control handles with a light ball. When used, the dual camera module is externally mounted on the head display. The dual camera captures the light ball of the control handle to determine the position of the handle in the space, and the handle Through BT to transmit its 6DOF information to the module, the module fuses the 6DOF and the position information of the ball to achieve omni-directional positioning, thereby improving the interaction of the first hand. The advantage of this solution is that under any ambient lighting conditions, the positioning accuracy is not affected by the ambient light, and the positioning accuracy is high. However, this solution cannot monitor and locate the overall space environment in which the user is located. It can only monitor the spatial position information of the photo ball handle, but its advantage is that the original VR device without space positioning can have at least similar HTC Vive. Spatial positioning capabilities.Ximmerse2. Outside-in space monitoring and positioning technologyOutside-in space monitoring and positioning technology is currently the VR device is a relatively mature space positioning technology, Sony PSVR and Oculus are based on a similar program, but Oculus is in an external infrared camera plus point initiative marks the way to get Higher accuracy and faster response time. The PS VR directly uses the PS 3's MOVE system. The principle is similar to that of the Kinect. An external binocular depth camera is used for motion recognition and tracking. There is a light indication on the head, and a different color light ball is at the top of the handle. The external dual camera checks the trajectory of the headlight and the ball on the handle at any time. At the same time, the PS StaTIon receives the IMU information of the head display and handle returned by the BT. , Through the calculation you can get a complete headshot and handle movement trajectory and positioning in space.PS StaTIonFrom the principle and the effect of actual use, the space monitoring and positioning precision of HTC Vive is not high, although Sony's gaming and PSVR wearing wearing their own moderate than Vive better, but the spatial positioning accuracy is not high, it affects the VR The overall experience of the game. So we see from Sony's official website a new spatial orientation of Sony patent, this patent is to be ready for the next generation of PVSR, from the description of the patent point of view should be similar to HTC's fixed laser emitters way, with this program The current practice of PSVR is the opposite. Instead of using an external camera to take pictures (outside-in positioning), the external VR signal is used to locate the direction of the VR helmet in space. This can provide similar HTC Vive usage accuracy (probably higher), and can capture the user's various poses and trajectories 360 degrees without dead ends.Outside-In positioningOculus space monitoring and positioning technology with Sony PSVR similar difference is PSVR camera uses a dual monitor visible external program, and is an active Oculus uses infrared light to the head and the handle are placed significant infrared emitting LED , Through an external infrared camera for shooting and capturing the headlights and infrared light spot information on the handle, so as to obtain head trajectory and handle movement trajectory and spatial position information.Whether it is Sony PSRV or Oculus's Outside-in program, there is a problem, that is, the external camera is fixed, and when the user is back to the camera, the camera can not detect the head and the handle on the light, may There is a possibility of missed supervision, thus affecting the user experience, which does not exist on the HTC Vive.Another Marker point-based Outside-in space monitoring and positioning technology is Ximmerse's photosphere with dual-camera solution. This is contrary to their previously mentioned Inside-out solution, where dual camera monitors have been placed. Indoor fixed position, and then put the ball in the VR head and handle, head and handle during the movement of a dual camera monitor recorded head and handle in the space of the three-dimensional position and their movement data, through BT or WiFi is passed to VR heads to perform related operations and processing, and feedback is implemented on the screen to allow them to freely move around in the virtual environment and interact with things in the virtual world.Lightball + Dual Camera SolutionAnalog of Lightball + Dual Camera SolutionHere is a video about Augmented Reality vs Virtual Reality:Augmented Reality vs Virtual Reality - AR vs VR | The Future ! | Tamil Tech  Book RecommendationVirtual, Augmented, and Mixed Realities in EducationThis book describes the current state of the art of various types of immersive learning: in research, in practice, and in the marketplace. It discusses advanced approaches in the design and development for various forms of immersive learning environments, and also the emerging innovations in assessment and research in the field.--by Dejian Liu, Chris Dede, Ronghuai Huang, John Richards Experience on Demand: What Virtual Reality Is, How It Works, and What It Can DoVirtual reality is able to effectively blur the line between reality and illusion, pushing the limits of our imagination and granting us access to any experience imaginable. With well-crafted simulations, these experiences, which are so immersive that the brain believes they’re real, are already widely available with a VR headset and will only become more accessible and commonplace. But how does this new medium affect its users, and does it have a future beyond fantasy and escapism?--by Jeremy Bailenson  Relevant information about "Research on Space Monitoring and Location Technology of AR&VR Equipment"About the article " Research on Space Monitoring and Location Technology of AR&VR Equipment", If you have better ideas, don't hesitate to  write your thoughts in the following comment area. You also can find more articles about electronic semiconductor through Google search engine, or refer to the following related articles. 

Today in this article we will discuss about how PCB is developed and its industrial trend. Printed circuit board, also called PCB, is an important electronic component and the support of electronic components, which also have a circuit in which a metal conductor can be connected to an electronic component. Nowadays electronic equipment requires high performance, high speed and thin miniaturization. As a multidisciplinary industry, PCB is the key technology of high-end electronic equipment. It plays an important role in electronic interconnection technology. Introduction to how PCB worksCatalogI PCB overviewII. Main types of PCB2.1 Single-sided boards2.2 Double-sided boards2.3 Multi-layer boardsIII Industrial chain of PCB3.1 Glass fiber cloth3.2 Copper foil3.3 Copper clad laminateIV Development of PCB industry in ChinaFAQI PCB overviewTraditional circuit boards are referred to as printed circuit boards because the circuit and its surface are created using the printing etching inhibitor method. At the moment, most circuit boards are made by using an etching inhibitor (film pressing or coating), and then etching is used to make the circuit board after exposure and development.Due to the continuous miniaturization and refinement of electronic products, most of the current circuit boards are coated with etching inhibitors (film pressing or coating). After exposure and development, the board will be etched to form the final circuit board. PCBs have progressed from single-sided to double-sided, multilayer, and flexible boards, and this trend is expected to continue. Because of its ongoing advancements in the areas of high precision, high density, and high reliability. PCB maintains a strong vitality in future electronic equipment development projects due to its continuous development of high precision, high density, and high reliability, reducing volume, cost, and improving performance.Printed circuit boardThe discussion of the development trend of the future PCB manufacturing technology at home and abroad is almost consistent, that is, developing toward the direction of high density, high precision, fine aperture, fine wire, fine spacing, high reliability, multilayer, high speed transmission, light weight and thin shape. At the same time, it is aimed to increase productivity, reduce costs, reduce pollution, adapt to multi-species and small run production during manufacturing. The technical development level of printed circuit is represented by the line width, aperture and the ratio of thickness to aperture of printed circuit.The creator of the printed circuit board was an Austrian called Paul Eisler. In 1936, he first used a printed circuit board in a radio. In 1943, Americans mainly applied this technology to military radios. Then in 1948, this invention was officially approved for commercial use in the United States.  Since the middle of 1950s, printed circuit boards have been widely used.Before the emergence of PCB, the interconnection of electronic components was accomplished by direct connection of electrical wires. Nowadays, wires exist only for laboratory applications. Printed circuit boards (PCB) have definitely occupied the position of absolute control in the electronic industry. II Main types of PCBAccording to the number of circuit layers, it can be divided into single-sided board, double-sided and multilayer board. The common multilayer board is usually 4 or 6 layers, and the complex multilayer board can have dozens of layers. Printed circuit boards are mainly divided into three types:2.1 Single-sided boardsOn the most basic PCB, the parts are concentrated on one side and the wire will be on the other (when there is patch element, it is on the same side as the wire, and the plug-in device is on the other side). Because the wire only appears on one side, this type of PCB is called single-sided board. The single-sided board has many strict restrictions on the design circuit (since there is only one side, the wiring cannot intersect and have to go around a separate path), so only the early circuits use this type of board.2.2 Doublesided boardsThere are wiring on both sides of this kind of circuit board.However, to use these two sides of the wire, you must have an appropriate circuit connection between the two sides. The "bridge" between these circuits is called “via”. The via hole is a small hole filled or coated with metal on the PCB, which can be connected to both sides of the wire. It can be connected to two sides of the wire. Because the area of the double-sided board is twice as large as that of the single panel,  it solves the difficulty of wiring interleaving in the single panel (it can get to the other side through the hole), so it is more suitable for the circuit which is more complicated than the single sided.2.3 Multi-layer boardsIn order to increase the area in which wiring can be made, the multilayer board is made up of more single or double-sided wiring boards. A printed circuit board with one side as the inner layer, two single sides as the outer layer or two sides as the inner layer, and two single sides as the outer layer, which is interlinked with conductive patterns according to the design requirements, is composed of four layers and six layers of printed circuit boards, also known as multilayer printed circuit boards (PCB). The number of layers on the board does not mean that there are several independent wiring layers. In special cases, an empty layer is added to control the thickness of the board, and the number of layers is usually even, and contains the outermost two layers. Most motherboards are 4 to 8 layers, but technically we can do nearly 100 layers of PCB. Large scale supercomputers mostly use quite many layers of motherboards. However, because such computers have been replaced by clusters of many common computers, super multilayer boards have been gradually unused. Because the layers in the PCB are tightly combined, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can see it. Also there are two kind of boards called rigid and flexible printed boards. > Rigid and Flexible Printed BoardsDivided into rigid circuit boards, flexible circuit boards and rigid-flexible printed circuit boards. The PCB shown in the first picture below is generally referred to as the rigid PCB, and the yellow connection line in the second picture is called flexible PCB. The intuitive difference between a rigid PCB and a flexible PCB is that the flexible PCB is flexible. The common thickness of rigid PCB is 0.2mm / 0.4mm / 0.6mm / 0.8mm / 1.0mm / 1.2mm / 1.6mm / 2.0mm etc. The common thickness of flexible PCB is 0.2mm. The thickening layer is added to the back where the parts are to be welded , and the thickness of the thickened layer varies from 0.2 mm to 0.4 mm. TThe purpose of understanding these is to provide them with a spatial reference for the design of a structural engineer. The common materials for rigid PCB include: phenolic paper laminates, epoxy paper laminates, Polyester glass felt laminates, epoxy glass cloth laminates; flexible PCB materials include: polyester film, polyimide film, ethylene propylene fluoride film.Rigid boardFlexible board III Industrial chain of PCBAccording to the upstream and downstream classification of the industrial chain, PCB industry can be divided into raw materials - CCL (copper-clad laminate) - PCB (printed circuit board) - electronic product application. The relationship is simply expressed as: 3.1 Glass fiber clothGlass fiber cloth is one of the raw materials of copper clad plate, which is made of glass fiber yarn and account for about 40% of the cost of copper clad laminate (thick plate) and 25% (thin plate). Glass fiber yarn is calcined into liquid state from raw materials such as silica sand in the kiln, then pulled into very fine glass fiber through extremely small alloy nozzles, and then hundreds of glass fibers are twisted into glass fiber yarn. The manufacture of glass fabric is similar to that of weaving enterprises. It can control production capacity and quality by controlling rotation speed, and the specifications are relatively single and stable. Since World War II, there has been almost no significant change in specifications.Unlike CCL, prices of glass fabrics are the most affected by supply and demand, fluctuating between $0.50-1.00 a meter in recent years. Taiwan and mainland China account for about 70% of the world's production capacity.3.2 Copper foilCopper foil is the raw material that accounts for the largest proportion of the cost of copper clad laminate, about 30% of the cost of copper clad plate (thick plate) and 50% (thin plate). Therefore the price increase of copper foil is the main driving force of the price increase of copper clad laminate. The price of copper foil is closely reflected in the change of copper price. However, the bargaining power is relatively weak. With the rising copper prices, copper foil manufacturers are in a difficult situation, and many enterprises have been forced to close down or be annexed. Even if copper clad laminate manufacturers accept copper foil price increases, copper foil manufacturers are still in a general loss. Another wave of price increases is likely to occur in the first quarter of 2006, possibly driving up CCL prices due to the price gap. 3.3 Copper clad laminateCopper clad laminate (CCL) is a direct raw material of PCB, which uses epoxy resin as fusion agent to press glass fiber cloth and copper foil to make printed circuit board (PCB) after etching, electroplating and multilayer laminate pressing. The copper clad laminate industry is not in high demand for capital, about 3 million to 40 million yuan, and can be stopped or converted at any time. In the upstream and downstream industrial chain structure, CCL has the strongest bargaining power. It has a strong voice in the procurement of glass fiber cloth, copper foil and other raw materials , and as long as the demand of downstream is good, the manufacturer of CCL can transfer the pressure of rising costs to the downstream PCB manufacturers. IV Development of PCB industry in ChinaThe development of PCB in China began in 1956. In 1963-1978, it is gradually expanded to be the PCB industry. More than 20 years after the reform and opening up, due to the introduction of foreign advanced technology and equipment, single-sided board, double-sided board and multi-layer board had a rapid development. The domestic PCB industry has gradually developed from small to large scale.Due to the concentration of downstream industries and relatively low labor and land costs, China has become the region with the strongest development momentum. In 2002, China became the third largest output country of PCB. In 2003, the output value and import and export volume of PCB exceeded $6 billion, which overtaking the United States for the first time and becoming the second largest output country in the world. The proportion of output value also increased from 8.54% in 2000 to 15.30%, nearly doubling. In 2006, China has replaced Japan as the world's largest PCB production base and the most active technology development country. China's PCB industry has maintained a high growth rate of about 20%, which is far higher than that of the global PCB industry. In terms of production composition, the main products of China's PCB industry have shifted from single-sided and dual-sided to multilayer, and are being upgraded from 4-6 layers to more than 6-8 layers. With the rapid growth of multilayer printed board, HDI board and flexible boards, China's PCB industrial structure is gradually being optimized and improved. However, although China's PCB industry has made considerable progress, there is still a big gap compared with advanced countries, and there is still much room for improvement in the future. First of all, China's entry into the PCB industry is relatively late and there are no specialized PCB research and development institution. There is a big gap between the research and development capabilities of some new technologies and foreign manufacturers. Secondly, in terms of product structure, the production of medium and low laminates is still dominated. Although FPC and HDI boards are growing rapidly, the proportion is still low because of its small base. Most of our PCB production equipment depends on imports, and some core raw materials can only rely on imports. The industrial chain is incomplete, which also hindered the domestic PCB series enterprise's development step.  FAQ 1. What is PCB?A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. 2. What is PCB and types of PCB?A printed circuit board (PCB) is a thin board made from fiberglass, composite epoxy, or other laminate materials. PCBs are found in various electrical and electronic components such as beepers, radios, radars, computer systems, etc. Different types of PCBs are used based on the applications. 3. What can a PCB be used for?Printed circuit boards (PCBs) are used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate, employed in the manufacturing of business machines and computers, as well as communication ... 4. Why are PCB green?It is due to the solder mask, which protects the copper circuits printed on the fibre glass core to prevent short circuits, soldering errors, etc. ... The colour of the solder mask gives the board its appearance. 5. What is PCB and its advantages?Compact Size and Saving of Wire. A characteristic PCB includes a large number of electronic components. On a Printed circuit board, the interconnection between the components is made through copper tracks instead of using a number of current carrying wires. It makes the interconnections less bulky. 6. How long does it take for PCBs to break down?3.5 to 83 days. The time it takes for half of the amount of PCBs (initially) present to be broken down ranges from 3.5 to 83 days for molecules with 1 to 5 chlorine atoms. In water, PCBs are essentially broken down by the effect of sunlight (photolysis). 7. What is the disadvantage of PCB?Disadvantages: Easy to Cause Handling Damage. Process Uses a Carcinogen (Thiourea) Exposed Tin on Final Assembly can Corrode. 8. Which PCB design software is the best for beginners?Top Best PCB Design Software of 2021a. PROTEL (Altium Designer) b.PADS (PowerPCB) c. ORCAD. d. Allegro. e. Eagle（Easily Applicable Graphical Layout Editor）f. Kicad.g. EasyEda.h. Fritzing. 9. What are the advantage of flexible PCB?The flexible circuit board are designed for saving room and improving the flexibility to meet a smaller and higher density mounting design, it also helps to reduce the assembly process and enhance reliability. 10. Why do we use PCB instead of breadboard circuit?The advantages of a printed circuit board: the board is permanent to have an electronic device worked. PCB has a better current carrying capacity comparing to a breadboard, you can make your traces wider to take more current so that work well. ... You can mount heat-sinks to the board so that have them rigid. 11. What PCB means?Printed-Circuit-BoardA printed circuit board, or PC board, or PCB, is a non-conductive material with conductive lines printed or etched. Electronic components are mounted on the board and the traces connect the components together to form a working circuit or assembly. 12. Why are PCBs dangerous for humans?PCBs are a probable human carcinogen.Studies of PCBs in humans have found increased rates of melanomas, liver cancer, gall bladder cancer, biliary tract cancer, gastrointestinal tract cancer, and brain cancer, and may be linked to breast cancer. 13. What are PCBs in electronics?A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. 14. Why are PCB green?It is due to the solder mask, which protects the copper circuits printed on the fibre glass core to prevent short circuits, soldering errors, etc. ... The colour of the solder mask gives the board its appearance. 15. What is PCB and its role?A process control block (PCB) is a data structure used by computer operating systems to store all the information about a process. It is also known as a process descriptor. When a process is created (initialized or installed), the operating system creates a corresponding process control block. 16. Which software is best for PCB design?- NI Multisim.- KiCad EDA.- Autodesk EAGLE.- DipTrace.- Ultiboard.- CAM350.- ExpressPCB Plus.- SolidWorks PCB. 

 There are a number of hot new technologies on the forefront of online and offline retail including machine learning, the Internet of Things (IoT) and Blockchain, the information-sharing technology behind Bitcoin.We have written a bit lately about machine learning because it perhaps has the highest “world-changing” potential. But the IoT – especially when it comes to radio frequency identification (RFID) – also has huge potential to transform any retail operation.RFID has been around for many years and has been adopted by a range of retailers including Walmart, Macy’s and Amazon. The way it works is simply that each product is given a radio frequency ID tag and that tag has its own unique magnetic signature. That signature is picked up by a receiver or “RFID reader” that not only records the unique ID, but also the location of the tagged product. RFID is also the same technology that you see on new tap-and-go credit cards.  Because the tags are read magnetically, it is a more efficient system than a typical visual scanning system because the tag and the reader do not need to be line-of-site to communicate.  Therefore, the immediate benefit for an RFID-based system is that a typical retailer can reduce the time required to take a typical physical inventory by something like 90 percent.  In other words, if it took 3 days to take an inventory using barcode scanning, that same inventory would take 45 minutes using RFID. RFID also increases accuracy substantially. Usually manual-scanned physical inventory has a 4 percent inaccuracy rate.  And that number is compounded throughout the year, so cycle counts done throughout the fiscal year can reach more than 60 percent inaccuracy by the holiday selling season. Conversely, RFID typically has less than a 0.5 percent inaccuracy rate, meaning that inventory is much more accurate throughout the year.Here are some more innovative uses for RFID: Adhering To The Master Merchandising Plan Most chain retail stores have their own planogram, designating where each product should go in the store. However, the more stores that a retail chain operates, the harder it is to get each store to execute the central buyer’s merchandise plan precisely. With enough readers placed in strategic locations throughout the store, most merchandise can be tracked within a very small area. This means that the central buyer can get a report of all of the misplaced merchandise in each store. This means that if a cellphone accessory is mistakenly placed in the video game section, it will show up on a report and can be immediately remedied in the field.  In addition, oftentimes products remain in the stockroom when in fact they should be out on the floor. A solid RFID system will be able to detect whether or not items are still in the backroom, where they probably won’t sell well. Inventory Accuracy – Improving Click & CollectMost retailers have an omnichannel strategy – meaning that customers can buy online and then pick up their orders in the store. Of course, this kind of click-and-collect strategy is predicated upon the accuracy of the inventory count in each store.  In other words, if the system says that there are two units of a certain SKU in a particular store, but actually there is an inaccuracy and there are zero, they will deliver a terrible customer experience when the customer shows up at the store only to find out that the product is not there. The far better accuracy of RFID will allow retailers to have a much greater confidence level that the product is actually in the place that the system says it is.  Understanding the Store’s Hot SpotsAnother benefit of RFID is that there is a record of where products are displayed in a store. And that record can be overlaid with sales data so that we understand what specific displays and traffic areas within the store deliver the most sales. Of course, different spots within a particular store may work better with some products than they do with others.  RFID technology can also help determine the best possible scenario when considering the SKU type, store type and display area. Fast & Accurate CheckoutOne of the most customer-facing use cases for RFID is being able to pay for the products much more quickly than ever before. With RFID, the cashier does not even need to take the products out of the customer’s basket in order ring them up in the system. The ability to skip the manual scanning process entirely makes a radical difference in wait times, especially during peak periods. In addition, RFID capability at checkout greatly reduces the cash reconciliation error at the register.  Detecting Fake Goods: A product’s legitimate manufacturer can embed an RFID tag into the product in a hidden place, allowing a reseller to scan for the signal to prove that the product is authentic. The trickier issue is whether or not the actual RFID tag can be forged, but that is fodder for another discussion. There are more and more companies that can deliver a range of RFID-related products and services, from hardware to full-blown systems.Kynix is one of them.  Ref. KY78-A4650KY78-B82450A2364A