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FPGA (Field-Programmable Gate Array), it is the product of further development on the basis of PAL, GAL, CPLD and other programmable devices. It appears as a kind of semi-custom circuit in the field of application specific integrated circuit (ASIC). It not only solves the shortage of custom circuit, but also overcomes the shortcoming of limited number of gates in the original programmable devices.What is an FPGA, and how does it compare to a microcontroller?CatalogI. What is FPGA?II. Principles of FPGAs III. FPGA Pros & ConsIV. FPGA Chip StructureV. FPGA FeaturesFAQI. What is FPGA?FPGA (Field Programmable Gate Array) is a product of further development on the basis of programmable devices such as PAL and GAL. It emerged as a semi-custom circuit in the field of application-specific integrated circuits (ASIC), which not only solves the deficiencies of custom circuits, but also overcomes the shortcomings of the limited number of gate circuits of the original programmable devices.II. Principles of FPGAs FPGA adopts the concept of Logic Cell Array (LCA), which consists of Configurable Logic Block (CLB), Input Output Block (IOB) and Internal Interconnect. Three parts. FPGAs are programmable devices with a different structure than traditional logic circuits and gate arrays (such as PAL, GAL and CPLD devices). The logic of the FPGA is implemented by loading programmed data into the internal static memory cell, and the values stored in the memory cell determine the logic function of the logic cell and the connection between the modules or between the modules and the I/O. The value stored in the memory cell determines the logical function of the logic unit and the way the modules are linked to each other or to the I/O, and ultimately determines the functions that the FPGA can achieve.III. FPGA Pros & Cons - The Pros of FPGAs:(1) FPGAs consist of hardware resources such as logic cells, RAM, multipliers, etc. By organizing these hardware resources rationally, hardware circuits such as multipliers, registers, address generators, etc. can be implemented.(2) FPGAs can be designed by using block diagrams or Verilog HDL, from simple gate circuits to FIR or FFT circuits.(3) FPGAs can be infinitely reprogrammed, loading a new design solution in a few hundred milliseconds, reducing hardware overhead with reconfiguration.(4) The operating frequency of the FPGA is determined by the FPGA chip as well as the design, and can be modified by modifying the design or replacing it with a faster chip to meet certain demanding requirements (of course, the operating frequency is not unlimited and can be increased, but is governed by current IC processes and other factors).  - The Cons of FPGAs:(1) All functions of FPGAs rely on hardware implementation and cannot implement operations such as branching conditional jumping.(2) FPGAs can only implement fixed-point operations.To conclude: FPGAs rely on hardware to implement all functions and can be compared to dedicated chips in terms of speed, but there is a big gap in design flexibility compared to general purpose processors.IV. FPGA Chip StructureMainstream FPGA is still based on look up table technology, has far exceeded the basic performance of previous versions, and integrates common features (such as RAM, clock management and DSP). FPGA chips have seven main parts: programmable input/ output unit, basic programmable logic unit, complete clock management, embedded block RAM, rich wiring resources, embedded bottom functional unit and embedded special hardware module.The functions of FPGA chip structure are as follows:1. Programmable Input and Output BlockThe programmable input/ output block is referred to as I/ O port. It is the interface part between the chip and the external circuit, which can drive and match the input/ output signals under different electrical characteristics. I/ O in FPGA is classified by group, and each group can support different I/ O standards independently. With the flexible configuration of the software, different electrical standards and I/ O physical characteristics can be met, the drive current can be adjusted, and the frequency of I/ O port of the and pull-up resistor and pull-down resistor can be changed, so that the frequency of the I/ O port can be higher and higher. Some high-end FPGA can support data rate up to 2Gbps through DDR register.Fig 1. IOB Internal Structure DiagramThe external input signal can be read into the FPGA through the memory cell of the IOB module, or directly written into the inside of the FPGA. When the external input signal passes through the memory cell of the IOB module read into the inside of the FPGA, the requirement of hold time  can be reduced, which usually the windows default is 0.In order to facilitate management and adapt to a variety of electrical standards, FPGA's IOB is divided into several banks, each bank interface standard is determined by its interface voltage VCCO, in addition, a bank can only have one VCCO, but each bank VCCO can be different. Only ports with the same electrical standard can be connected together, and the same VCCO voltage is the basic requirement of the interface standard.2. Configurable Logic Block (CLB)CLB is the basic logical unit within the FPGA. The actual number and characteristics of CLBs vary depending on the device, but each CLB contains a configurable switch matrix that consists of 4 or 6 inputs, some lectotype circuits (multiplexers, etc.) and flip-flops. The switch matrix is highly flexible and can be configured to work with combinational logic, shift registers, or RAM. In Xilinx's FPGA device, the CLB consists of multiple (usually 4 or 2) identical Slices and additional logic. Each CLB module be used to realize combinational logic and sequential logic, and it can also be configured as distributed RAM and distributed ROM.Fig 2. CLB Structure DiagramSlice is a basic logical unit defined by Xilinx. A Slice consists of two 4-input functions, carry logic, arithmetic logic, storage logic and function multiplexer. Arithmetic logic includes a  XORG and a MULTAND. XORG enables a Slice to implement the full operation of 2bit, and MULTAND improves the efficiency of multipliers. Carry logic consists of a dedicated carry signal and a function multiplexer for fast arithmetic addition and subtraction operations; 4-input functions generator is used to implement the 4-input LUT, distributed RAM or 16-bit shift register. Carry logic includes two fast carry chains to improve the processing speed of the CLB module.Fig 3. Inputting Slice Structure Diagram3. Digital Clock Management (DCM)Most of the industry's FPGA offer digital clock management. FPGA offers digital clock management and phase loop locking. Phase loop locking can provide accurate clock synthesis, reduce jitter and achieve filtering.4. Block Random Access Memory (BRAM)Most FPGAs have embedded block RAM, which greatly extends the applications and flexibility of the FPGA. The block RAM may be configured as a single-port RAM, a dual-port RAM, a content address memory (CAM), and a common storage structure such as a FIFO. CAM memory has a comparison logic in each of its internal memory cells, the data written into the CAM will be compared with each of the data in the interior, and the address of all data that is the same as the port data, so that there is a wide range of address switches in the route application. In addition to the block RAM, the LUT in the FPGA can be flexibly configured as a RAM, a ROM, and a FIFO. In practical application, that number of block RAM in the internal block of the chip is also an important factor in the chip selection.The capacity of the monolithic RAM is 18k bits, that is, the bit width is 18 bits and the depth is 1024. It can change the bit width and depth according to the need, but two principles must be satisfied: firstly, the modified capacity (bit width depth) cannot be greater than 18k bits; Second, the maximum bit width cannot exceed 36 bits. Of course, it is possible to concatenate multiple blocks of RAM to form a larger RAM, which is limited only by the number of RAM blocks in the chip and is no longer constrained by the above two principles.5. Wiring SourceAll the parts are connected with wiring resources in the FPGA, and the length and process of the connection determine the driving ability and the transmission speed of the signal on the wire. There are abundant wiring resources in the FPGA chip, according to the process and length, width and distribution position, which are divided into 4 different categories. First is the global routing resource, which is used for the internal global clock and the global reset/ position routing. Second is the long line resource, which is used to complete the wiring of the high-speed signal and the second global clock signal between chip banks. Third is short-line resources, which are used to perform logical interconnection and cabling between basic logical units. Fourth is a distributed wiring resource, which is used as control signal lines for a proprietary clock or a reset.In practice, the designer does not need to select the routing resources directly, and the layout scheduler can automatically select the better routing resources according to the topology of the input logical grid table and constraint conditions to connect each module unit. In essence, the use of routing resource types has a close and direct relationship with the results of the design.6. Underlying Built-in Function The underlying built-in function mainly refers to a DLL (Delay Locked Loop), a PLL (Phase Locked Loop), a DSP, and a CPU, which belong to core softcore. The more and more built-in functional units make the single-chip FPGA a system-level design tool, so that it has the capability of joint design of hardware and software, and gradually turn to the SOC platform.DLL and PLL have similar functions, such as high-precision clock and low jitter frequency doubling and frequency division, duty cycle adjustment and phase shift, etc. Xilinx integrated the DLL, Altera made the PLL, Lattice combined both two, which can be easily managed and configured through IP core-generated tools on Lattice's new chip. Fig 4. Typical DLL module schematics7. Special Built-in Hard CoreThe embedded special hard core is relative to the soft core embedded in the bottom, which means that the hard core with strong processing ability of FPGA is equivalent to the ASIC. To improve FPGA performance, chip manufacturers integrate some dedicated hard cores on the chip. For example, to improve the multiplication speed of FPGA, special multipliers are integrated in the mainstream FPGA, and in order to match the communication bus and interface standard, a lot of high-end FPGA are integrated SERDES, which can achieve the receiving and dispatching speed of  Gbps. V. FPGA Features1) The ASIC circuit is designed by adopting the FPGA, and the user does not need to put the chip into production, so that a shared chip can be obtained.2) FPGA can be used as a trial sample of other fully customized or semi-custom ASIC circuits.3) There are rich flip-flops and I/ O pins within the FPGA.4) FPGA is one of the devices with the shortest design cycle, the lowest development cost and the least risk among ASIC circuits.5) FPGA adopts high-speed CMOS process, low power consumption, and can be compatible with CMOS and TTL.It can be said that FPGA chip is one of the best choices for small batch system to improve system integration and reliability.The working state of FPGA is set by the program stored in the on-chip RAM, so it is necessary to program the on-chip RAM when working. Users can use different programming methods according to different configuration modes.When the power is on, the FPGA chip reads the data from the EPROM into the on-chip programming RAM. After the configuration is completed, the FPGA enters the working state. After power off, FPGA internal logic disappears. Therefore, FPGA can be programmed repeatedly. And the programming of FPGA does not require a special programmer, a general-purpose EPROM or PROM programmer can meet the requirement. When you need to modify the FPGA functionality, just replace a piece of EPROM. In this way, the same piece of FPGA, with different programming data, can produce different circuit functions. Therefore, the use of FPGA is very flexible.FAQ 1. What is FPGA and why it is used?FPGA Basics: Architecture, Applications and Uses. The field-programmable gate array (FPGA) is an integrated circuit that consists of internal hardware blocks with user-programmable interconnects to customize operation for a specific application.2. Is FPGA faster than CPU?They also found that using custom FPGAs to implement the Rowhammer exploit would cause far more of the "bit flips" that they wanted to see. A FPGA can hit the data cell faster and more often than a CPU can do it meaning the FPGA causes more results to occur during an attack. It all goes faster when an FPGA is used.3. Are FPGAs dead?Yes, it's a dead end. If you enjoy creating hardware, RTL design targeting FPGAs is still a good choice (although there is a huge amount of effort here to make it more like creating software than hardware).4. What are FPGAs good for?FPGAs are particularly useful for prototyping application-specific integrated circuits (ASICs) or processors. An FPGA can be reprogrammed until the ASIC or processor design is final and bug-free and the actual manufacturing of the final ASIC begins. Intel itself uses FPGAs to prototype new chips.5. Is FPGA a microprocessor?Microprocessors are more complex than FPGAs. Microprocessors have fixed instructions while FPGAs don't. FPGAs and microprocessors are often mixed into a single package.6. What are the advantages of FPGA?FPGA advantages:Long-term availability.Updating and adaptation at the customer.Very short time-to-market.Fast and efficient systems.Acceleration of software.Real-time applications.Massively parallel data processing.7. Why is FPGA slow?FPGAs tend to get faster in max speed, but the limit actually has to do with process variation affecting static timing. The chips have to have a soultion that works on all of them. So you lose performance of the device to make sure any device will work with it. And as your design gets bigger it runs slower.8. What are the disadvantages of FPGA?Drawbacks or disadvantages of FPGA:The programming is not as simple as C programming used in processor based hardware. Moreover engineers need to learn use of simulation tools. ➨The power consumption is more and programmers do not have any control on power optimization in FPGA. No such issues in ASIC.9. Can FPGA replace CPU?There will always be a need for a general purpose CPU to run most things, and while you can implement a CPU on an FPGA, that gives you the worst of both worlds - no improvement from specialised hardware design, and you still need to pay the “FPGA tax”. So no, FPGAs will never replace CPUs.10. Why use an FPGA vs microcontroller?A FPGA can be used if the design requires complex logic and requires high processing ability and if the cost is comparable to the performance achieved. In case of a design that requires limited hardware, and is set to perform only some specific functions, then Microcontroller is preferred.

What is a resistor? In short, resistors are electronic components which have a specific, never-changing electrical resistance. The resistor's resistance limits the flow of electrons through a circuit. So in this article today, we will have a detailed discussion on resistors, which will present you as much as information about resistor as possible.I What is a Resistor?1.1 Brief IntroductionResistors are passive electrical components that limit electric current. This video explains in an easy way the most basic background to help you understand resistors and use them.A resistor refers to a two-terminal electronic element made of resistor material with a certain structure that can limit the current passing through the circuit. It is the most widely used component in electronic circuits, which usually form different series according to its power and resistance values. Its function in circuits is to regulate and stabilize current and voltage, that is,  used as shunt and voltage divider, or circuit matching load. According to the circuit requirements, it can also be used for negative feedback or positive feedback of amplifying circuit, voltage-current conversion, voltage or current protecting element when existing input overload. With the capacitor, it can form an RC circuit, which can be used as oscillation, filter, bypass, differential, Integral and time constant elements, etc. Those whose resistance values cannot be changed are called fixed resistors, and those with variable resistance values are called potentiometers or variable resistors. Some special resistors, such as thermistors, varistors, and sensitive elements, have a nonlinear relationship between voltage and current.1.2 Resistor and ResistanceThe resistor is a current limiting element in daily life. Resistance is a physical quantity describing the conductivity of a conductor, represented by R. Resistance is defined by the ratio of the voltage U at the two ends of the conductor and the current I passing through the conductor, that is, R=V/I. When the resistor is connected to the circuit, the resistor's resistance is fixed by two pins, which can limit the current to flow through the branch of the resistor. The resistance that cannot be changed is called a fixed resistor. In addition, a variable resistance is called a potentiometer or a variable resistor. The ideal resistor is linear, that is, the instantaneous current of the resistor is positive to the applied instantaneous voltage, for example, the variable-voltage resistor is used as a voltage divider. On a bare resistor, there are one or two removable metal contacts, and the contact position determines the resistance between any end of the resistor and the contact.  The terminal voltage and current have a definite function relation, and the two-terminal device which embodies the conversion of electric energy into other forms, represented by the letter R, and its unit is Ω. Devices such as light bulbs, heating wires, resistors, and so on can be expressed as resistor elements.The resistance value of the resistor is generally related to temperature, material, component length, and cross-section area. The physical quantity of measuring resistance affected by the temperature is the temperature coefficient, which is defined as the percentage of resistance value changing when the temperature rises 1℃. The main physical characteristic of resistors is transforming the electricity into heat energy, also the resistor can be said to be an energy dissipation element because the internal energy will be generated when current flows through it. Resistors usually act as a divider and shunt in a circuit. And for signals, both AC and DC signals can pass through resistors.In physics, resistance is a figure to indicate the magnitude of a conductor's hindrance to current. The greater the resistance of a conductor, the greater the resistance of the conductor to the current. Generally, different conductors have different resistances, in other words, resistance is a characteristic of the conductor itself. The resistance element is a kind of energy dissipation element which hinders the current. The stuff under the action of matter called resistive substance because of its blocking effect on the current. The resistor will lead to the change of the electron flux. When the voltage at both ends of the conductor is fixed, the larger the resistance, the smaller the current passing through, on the other hand, the smaller the resistance, the greater the current passing through. 1.3 Resistor BasicsThe resistor consists of three parts of a resistor body, a framework, and a lead-out end (the resistor body of the solid-core resistor is integrated with the framework), and the resistor body plays an important part in this electronic component. For a resistor body with a uniform cross-section, the resistance value is calculated by the following formula: ρ is the electrical resistivity (ohm-cm), L is the length (cm) of the resistor, and A is the cross-sectional area of the resistor (square centimeter).R=ρ× L/AThe thickness of the thin film resistor is very small and difficult to measure accurately, and ρ varies with the thickness values, so the constant related to the film material is regarded as the film resistance. In fact, it is the resistance of the square film, so it is also known as the square resistance. For homogeneous films, W is the width of the film (cm), in general, Rs should be in a limited range because large Rs will affect the stability of resistor performance. Therefore the cylindrical resistor is notched and the planar resistor uses the etching method of a detour to extend the range of resistance and to fine-tune the resistance.R=Rs×L/WThe volt-ampere characteristic is a graph that represents the relationship between the voltage and the current of the resistor terminal. When the voltage-current is proportional (representing a straight line), it is called a linear resistor, otherwise referred to as a non-linear resistor.The vertical coordinates of this diagram are current I and the transverse coordinates are voltage U. This graph is also called the current-voltage curve, more often is referred to as the volt-ampere characteristics curve. As we can see, the blue curve is a straight line passing through the origin, and its resistance does not change with the change of voltage and current, in fact, elements that satisfy this volt-ampere characteristic curve are called linear elements. On the other hand, for the red curve, we can see that it is a curve, its resistance value changes with the change of voltage and current.The main parameters used to characterize the resistance have nominal resistance, allowable deviation, rated power, load characteristic, resistor temperature coefficient, and so on.1.4 Resistor Operation TheoryOhm's lawThe behavior of an ideal resistor is dictated by the relationship specified by Ohm's law:V=I ∙ ROhm's law states that the voltage (V) across a resistor is proportional to the current (I), where the constant of proportionality is the resistance (R). For example, if a 300-ohm resistor is attached across the terminals of a 12-volt battery, then a current of 12/300 = 0.04 amperes flows through that resistor.Practical resistors also have some inductance and capacitance which affect the relation between voltage and current in alternating current circuits.In addition, linear or ohmic resistance meets Ohm's law, but nonlinear resistance does not satisfy Ohm's law.The nominal resistance is the design resistance of the sign on the resistor with a digital or color code. The units are Ω, KΩ, and MΩ. Resistance values are written according to standardized priority series, which correspond to allowable deviations.The electrical resistance of a resistor is measured in ohms. The symbol for an ohm is the greek capital-omega: Ω. The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured over a very large range of values, the derived units of milliohm (1 mΩ = 10−3 Ω), kilohm (1 kΩ = 103 Ω), and megohm (1 MΩ = 106 Ω) are also in common usage. For example, a 4,700Ω resistor is equivalent to a 4.7kΩ resistor, and a 5,600,000Ω resistor can be written as 5,600kΩ or (more commonly as) 5.6MΩ. 1.5 Resistor Electronic SymbolsNotation1Ω= 1 Ohms1 KΩ= 1 Kilo Ohms1 MΩ= 1 Mega Ohms1 GΩ= 1 Giga OhmsWhen the value can be expressed without a prefix (that is, multiplicator 1), an "R" is used instead of the decimal separator. For example, 1R3 indicates 1.3Ω, and 15R indicates 15Ω.Marking method for Resistance and Tolerance of Resistors：① Direct Scaling MethodThe resistance and error of the resistor are directly printed on the resistor by numbers and letters (no error is indicated as the tolerance ±20%). There are also manufacturers who use customary marking methods, such as:3Ω3Ⅰis represent the resistance 3.3Ω, tolerance is ±5%1 K 8 represents the resistance 1.8 KΩ, tolerance is ±20%5 M 1Ⅱis represent the resistance 5.1 MΩ, tolerance is ±10% ② Resistor Color Bands/CodesThis Physics video tutorial is explaining the fundamentals of color code for four colour bands in a carbon resistor.The color bands are coated on the resistor to indicate the nominal value of the resistor and the allowable tolerance. The corresponding values of various colors and the recognition rules of the color bands/codes of the reading principle of the fixed resistor are shown in the following figure.Four-band ResistorsIn the standard four-band resistors, the first two bands indicate the two most significant digits of the resistor’s value. The third band is a weight value, which multiplies the two significant digits by a power of ten.The final band indicates the tolerance of the resistor. The tolerance explains how much more or less the actual resistance of the resistor can be compared to what its nominal value is. No resistor is made to perfection, and different manufacturing processes will result in better or worse tolerances. For example, a 1kΩ resistor with 5% tolerance could actually be anywhere between 0.95kΩ and 1.05kΩ.Example: red-orange black gold=23*10^0=23Ω(±5%)Five-band and six-band ResistorsFive band resistors have a third significant digit band between the first two bands and the multiplier band. Five band resistors also have a wider range of tolerances available.Six band resistors are basically five band resistors with an additional band at the end that indicates the temperature coefficient. This indicates the expected change in resistor value as the temperature changes in degrees Celsius. Generally, these temperature coefficient values are extremely small, in the ppm range.Example: red blue green black brown=265*10^0=265Ω(±1%)ToleranceThe maximum tolerance between the actual resistance and the nominal resistance, represented by percentages. Commonly used are ±5%, ±10%, ±20%, precision is less than ±1%, high precision up to 0.001%. The accuracy is determined by both the tolerance and the irreversible resistance.Power RatingMaximum power dissipation allowed for continuous operation of resistors at rated temperature (maximum ambient temperature) tR. And the maximum operating voltage is also specified for each resistor, that is, the maximum operating voltage cannot be exceeded even if the resistance value is high.Identification of rated Power of ResistorsThe rated power of a resistor refers to the maximum power that a resistor is allowed to consume in a long-term continuous operation in a DC or AC circuit. There are two marking methods: the resistance above 2W is directly printed on the resistor body, and the resistance below 2W is represented by its own volume. When the resistance power is expressed on the circuit diagram, the following symbols are used: 1) Load CharacteristicWhen the working temperature is lower than tR, the resistor can not exceed its rated power, and the load power must be reduced when it exceeds tR. Each resistor has its own specified load characteristic. In addition, the load is allowed to be reduced accordingly at low pressure. Under pulse load, the average power of the pulse is much lower than the rated power, the load is according to the practical situation.2) Resistance Temperature CoefficientThe average relative variation of the resistance value at each change of 1℃ is expressed in terms of ppm/ ℃ within a specified range of ambient temperature. In addition to the above parameters, there are other technical indicators, such as nonlinearity (the extent to which the characteristics of the current and the applied voltage deviate from the linear relationship), the voltage coefficient (the relative rate of change of the voltage at which the voltage is applied, the relative rate of change of the volt resistance), current noise (the ratio of the effective value of the noise potential generated by the current flow in the resistor to the measured voltage, expressed by the current noise index), the high-frequency characteristic (due to the effect of the distributed capacitance and the distributed inductance in the resistor; a curve in which the resistance value decreases as the operating frequency increases; long-term stability (such as irreversible changes in resistance values affected by environmental conditions during long term use or storage).II Resistor CharacteristicsDependent on the application, the electrical engineer specifies different properties of the resistor. The primary purpose is to limit the flow of electrical current; therefore the key parameter is the resistance value. The manufacturing accuracy of this value is indicated with the resistor tolerance in percentage. Many other parameters that affect the resistance value can be specified, such as long-term stability or the temperature coefficient. The temperature coefficient, usually specified in high precision applications, is determined by the resistive material as well as the mechanical design.In high-frequency circuits, such as in radio electronics, the capacitance and inductance can lead to undesired effects. Foil resistors generally have a low parasitic reactance, while wire-wound resistors are amongst the worst. For accurate applications such as audio amplifiers, the electric noise must be as low as possible. This is often specified as microvolts noise per volt of applied voltage, for a 1 MHz bandwidth. For high-power applications, the power rating is important. This specifies the maximum operating power the component can handle without altering the properties or damage. The power rating is usually specified in free air at room temperature. Higher power ratings require a larger size and may even require heat sinks. Many other characteristics can play a role in the design specification. Examples are the maximum voltage or the pulse stability. In situations where high voltage surges could occur this is an important characteristic.Resistors in series and parallel ConnectionIn electronic circuits, resistors are very often connected in series or in parallel. A circuit designer might for example combine several resistors with standard values (E-series) to reach a specific resistance value. For series connection, the current through each resistor is the same and the equivalent resistance is equal to the sum of the individual resistors. For parallel connection, the voltage through each resistor is the same, and the inverse of the equivalent resistor value is equal to the sum of the inverse values for all parallel resistors. In the articles resistors in parallel and series, a detailed description of calculation examples is given. To solve even more complex networks, Kirchhoff’s circuit laws may be used.The Total resistance of resistors connected in series is the sum of each single individual resistance value.The total resistance of resistors connected in parallel is the reciprocal of the sum of the reciprocals of the individual resistors.As a special case of this equation: if you have just two resistors in parallel, their total resistance can be calculated with this slightly-less-inverted equation:Termination and MountingResistors will come in one of two termination types: through-hole or surface-mount. These types of resistors are usually abbreviated as either PTH (plated through-hole) or SMD/SMT (surface-mount technology or device).Through-hole resistors come with long, pliable leads which can be stuck into a breadboard or hand-soldered into a prototyping board or printed circuit board (PCB). These resistors are usually more useful in breadboarding, prototyping, or in any case where you’d rather not solder tiny, little 0.6mm-long SMD resistors. The long leads usually require trimming, and these resistors are bound to take up much more space than their surface-mount counterparts.The most common through-hole resistors come in an axial package. The size of an axial resistor is relative to its power rating. A common 1/2W resistor measures about 9.2mm across, while a smaller 1/4W resistor is about 6.3mm long.Surface-mount resistors are usually tiny black rectangles, terminated on either side with even smaller, shiny, silver, conductive edges. These resistors are intended to sit on top of PCBs, where they’re soldered onto mating landing pads. Because these resistors are so small, they’re usually set into place by a robot and sent through an oven where solder melts and holds them in place.III Resistor TypesMost types of the resistor are linear devices that produce a voltage drop across themselves when an electrical current flows through them because they obey Ohm’s Law, and different values of resistance produce different values of current or voltage. This can be very useful in Electronic circuits by controlling or reducing either the current flow or voltage produced across them we can produce a voltage-to-current and current-to-voltage converter.Resistors come in a variety of shapes and sizes. They might be through-hole or surface-mount. They might be a standard, static resistor, a pack of resistors, or a special variable resistor. The different types of resistors are discussed in the following section.1. Classified by Volt-ampere Characteristic*Linear resistors*Non-linear resistorsFor most conductors, at a certain temperature, the resistance is almost unchanged and is a certain value, the resistors having this kind of resistance is called a linear resistor. The resistors of some materials vary obviously with the current (or voltage) change, and the volt-ampere characteristic of them is a curve, which is called a nonlinear resistor. Under a given voltage (or current), the ratio of voltage to current is the static resistance at the working point, and the slope on the voltage-ampere characteristic curve is dynamic resistance. The expression of nonlinear resistance characteristics is complicated, but these nonlinear relations are widely used in electronic circuits.2. Classified by Material1) Wirewound resistor is made of resistive wires, wound high resistance alloy wires on an insulating skeleton, and coated with a heat-resistant glaze insulating layer or insulating paint. The wire-wound resistor has a low-temperature coefficient, high resistance accuracy, good stability, sound heat resistance, and corrosion resistance. It is mainly used for precise and high power resistance. The shortcoming is that the high-frequency performance is poor and the time constant is large.  ApplicationsIt has high securityAccurate measurement and balance current control is required.2) The carbon composition resistor is made from the mixer of granulated or graphite, an insulation filter, and a resin binder. The actual resistance of the resistor is determined by the ratio of the insulation material. The shape of the insulating binder is in the shape of roads and there are two metal caps at both the end of the roads. At both ends of the resistor, it has two wire conductors for easy connectivity in the circuit design. There are different colors that are printed on the resistor to find the value of it and the road is covered with the plastic coat.   ApplicationsThe composition resistor is used in the high energy pulses.·It has a relatively small size.·High voltage power supplies·Welding·High power3) A carbon film resistor is plated with a carbon layer on the porcelain tube, and the crystalline carbon is deposited on the ceramic rod framework. Furthermore, the temperature coefficient is from -100 to -900 ppm/°C. The carbon film resistor has the advantages of low cost, stable performance, wide resistance range, low-temperature coefficient, and low voltage coefficient, and is the most widely used resistor.  ApplicationsThe carbon film resistors are available in High plus stability.4) A metal film resistor is coated with a layer of metal on the ceramic tube, and the alloy material is plated on the surface of the ceramic rod skeleton by vacuum evaporation.Metal film resistor is more accurate than carbon film resistor, other advantages such as good stability, small noise, low-temperature coefficient. It is widely used in instrumentation and communication equipment.5) Metal oxide film resistors are coated with tin oxide on the ceramic tube, and a layer of metal oxide is deposited on the insulating rod. Because its body is an oxide, so it has high temperature stability, heat shock resistance, sound load capacity. According to the purpose, it is divided into universal, precision, high frequency, high voltage, high resistance, and high power type, also it can forms resistors network.IV Special Resistors1) KNP-RF: it also called a fuse resistor, which functions like a resistor and a fuse in the normal condition. When the circuit fails to make the power exceed the rated power, it will be blown as if the fuse is blown and the connection circuit is disconnected. The general resistance of the fuse resistance is small (0.33Ω ~ 10KΩ), and the power is also small. The common types of fuse resistors are RF10 type, RF111-5 fuse resistor symbol type, RRD0910 type, RRD0911 type, etc.2) Sensitive resistor: a resistor whose resistance value is sensitive to certain physical quantities (such as temperature, humidity, light, voltage, mechanical force, gas concentration, etc.). When these quantities change, The resistance value of the sensitive resistors will change with the change of physical quantity, showing different resistance values. According to the sensitivity to different physical quantities, the sensitive resistor can be classified as heat-sensitive, humidity-sensitive, photosensitive, pressure-sensitive, force-sensitive, magnetic sensitive, and gas sensitive. Sensitive resistors are almost made of semiconductor materials, thus they are also known as semiconductor resistors.The resistance of the thermistor varies with the change of temperature, when the temperature rise, this resistor is a negative temperature coefficient (NTC) thermistor. In most cases, the NTC thermistor is widely used, according to its different use, it can be divided into common NTC thermistor, steady-voltage NTC thermistor, thermometric NTC thermistor, and so on. The resistance of the photosensitive resistor changes with the intensity of the incident light. When the incident light is enhanced, the resistance decreases and the resistance increases when the incident light weakens.V How to Select a Suitable Resistor1) There are many types of fixed resistors, what materials and structures should be selected, it is necessary to consider the specific requirements of the application circuit. In high-frequency circuits, non-wire-wound resistors with small distributed inductance and capacitance should be selected,  such as carbon film resistor, metal resistor, and metal oxide film resistor, thin-film resistor, thick film resistor, alloy resistor, corrosion-resistant film resistor, etc. In high gain and small-signal amplifying circuits, low noise resistors should be used, such as metal film resistors, carbon film resistors, and wire-wound resistors, rather than synthetic carbon film resistors and organic solid resistors with high noise.There are different types of the resistor which are in the following:Carbon compositionCarbon PileCarbon filmPrinted carbon resistorThick and thin filmMetal filmMetal oxide filmWire woundFoil resistorAmmeter shuntGrid resistorSpecial veritiesLed ArrangementThe resistance value of the selected resistor shall be close to a nominal value of the calculated value in the application circuit, and the standard series resistor shall be preferred. The tolerance of resistors used in general circuits is ±5%~±10%. Precision resistors should be used in precision instruments and special circuits, with precision within 1%, such as 0. 01%, 0.1% or 0. 5% tolerance. The rated power of the selected resistor should not be arbitrarily increased or reduced in order to meet the requirements of the power capacity of the resistor in the application circuits.If the circuit is required to be a power resistor, the rated power can be 2 times higher than that required by the practical application circuit.Selection of Fuse ResistorFuse resistor, a kind of resistor with a protective function. The dual performance should be considered and the parameters such as resistance and power should be selected according to the specific requirements of the circuits. It is not only to ensure that it can fuse quickly when it is overloaded but also to guarantee that it can work stably for a long time under normal conditions. In addition, if the resistance is too high or the power is too large, it can not play a protective role either.Three basic principles for the selection of resistors:Select high-level standard resistors manufactured by a production line certified by the certification administrations.Select resistors manufactured by manufacturers with advantages of function, quality, efficiency,  price, and service.Select the manufacturer who meets the above requirements.VI Things Needing AttentionThe resistors should be checked before use, checking their performance is to measure whether the actual resistance value is consistent with the nominal value and whether the error is within the allowable range. The method is to measure the resistance by the multimeter.Two points need to pay attention to when measuring.1)The range should be determined according to the measured resistance when the pointer is indicated in the middle of the scale, which is easy to observe.2)After determining the resistor range, having zero adjustments is that the two table pens are directly touching (short circuit), that is, the "zero adjustments" device is adjusted so that the pointer is accurately pointed to the "0" of the Ω scale, and then the resistance value is measured again. Also, be careful not to touch both ends of the resistor or the metal part of the pen, otherwise, the test error will be caused.If the resistance measured by the multimeter is close to the nominal value, the basic quality is good, and if the difference is big or the multimeter does not work at all, this resistor is bad.VII Resistor Detection1. Appearance CheckFor a fixed resistor, check the logo clear firstly: intact protective paint, no charring, no scars, no cracks, no corrosion, resistive body and pin connected closely. For potentiometers, the axis flexible, proper tight, the comfortable handle should be the key point. If there is a switch, checking the switch whether is working properly.2. Multimeter Detection① detection of fixed resistanceWhen measuring, the different resistances are measured by the proper electric gears of the multimeter. For the pointer type multimeter, because the indicator of electric gear is nonlinear, the larger the resistance value, the more dense the indicator number is, so the more accurate the reading is, the larger the angle of needle deviation should be, to make more accurate reading numbers. If the measured result exceeds the error range of the resistor, the resistance value is infinite, unstable, or zero, which indicates that the resistor has been broken.In the measuring process, the hands holding the resistor should not contact the two pins of the resistor, which will affect the accuracy of the measurement. In addition, the multimeter can not be used to detect the resistance during power on, because online detection shouldn’t be allowed.② Detection of fuse resistors and sensitive resistorsThe resistance range of fuse resistors is generally only a few to dozens of Ω. If the detecting resistance is infinite, it indicates that the fuse has been fused. The resistance can also be measured online, measuring the grounding voltage at both ends respectively, if one end is equal to the power supply voltage and another end voltage is 0V, indicating the fuse resistor has broken.There are many kinds of sensitive resistors, in this section, taking thermistors as an example. As above mentioned, it is divided into positive temperature coefficient(PTC) thermistors and negative temperature coefficient(NTC) thermistors. For the PTC thermistor, the resistance value is usually small at normal temperatures. In the measurement, when using the electric soldering iron with burning heat close to the resistor, the resistance value will be obviously increased, which indicates the resistor is normal, and if no change appears, indicating the component is damaged. The NTC thermistor is the opposite.Under the circumstance without light, the resistance value of light-sensitive resistors is large, on the contrary, the measuring resistance will be reduced obviously when there is light, if there is no change, the component is damaged.③ Detection of variable resistors and potentiometerFirstly, measuring whether the resistance values between the two fixed ends are normal, if the detecting values are infinite or zero, or is larger or small than the nominal values, exceeding the tolerances, which indicates the device is damaged. If the resistance value of the resistive body is normal, then a meter pen of the multimeter is connected with the sliding end of the potentiometer, the other pen is connected with any fixed end of the potentiometer (adjustable resistor), and the footstalk is slowly rotated to observe whether the meter needle is stably changed.when the resistance value is changed from zero to the nominal value (or vice versa) from one end to the other end, and there is no jump or jitter in the course of rotation, which indicating the potentiometer is normal, if any, it is indicated that the sliding point of resistance is in poor contact3. Measuring resistance with bridgeIf the accurate measurement of resistor resistance is required, it can be measured by a bridge (digital). The resistance can be read from the display by inserting the resistor into the measuring end of the bridge by selecting an appropriate range. For example, when a resistor is made from a wire or a fixed resistor is processed to obtain a more accurate resistance value, under this situation, the resistance of the self-made resistor must be measured by a bridge.Different applications, the purpose of applying varistor, different voltage/current stress acting on the varistor, so the requirements for the varistors are different, thus it is necessary to pay attention to detecting. According to the purpose of the application, the varistors can be divided into two categories: the protection varistor and the circuit function varistor.1) Distinguish between the power supply, signal lines, and data wire protection for varistors, because they should meet the requirements of different technical standards.2) According to the difference of the continuous working voltage applied on the varistors, the power lines can be divided into two types: AC or DC, in addition, the aging characteristics of varistors under these two voltage stresses are different.3) According to the abnormal overvoltage of varistors, it can be divided into three types: surge suppression type, high power type, and high energy type.Surge suppression type: it is used to suppress transient overvoltages caused by lightning and improper operation. Transient overvoltages are random, aperiodic, and the peak value of current voltages may be very large.High power type: it is used to absorb a continuous group of pulses occurring in a period, for example, a varistor connected to a switching power converter, where the impulse voltage period occurs, and the period is knowable, so the energy value can generally be calculated. From this, we can see the peak value of voltage is not large, but occurs frequently, thus its average power is quite large.High energy type: it is used to absorb magnetic energy in large inductance coils such as generator excitation coils, lifting electromagnet coils, etc. For such applying requirements, the main technical index is energy absorption capacity.The protection of varistor can be used repeatedly in most applications, but sometimes it can be made into a one-off protection device such as a current fuse. For example, a varistor with short-circuit contact connected to a load of some current transformers. VIII How to Recognize a Resistor1. Color bands resistorThe first and second bands with four color bands represent the first two digits of the resistance respectively; the third band represents the multiplier; the fourth band represents the tolerance.   ColorDigitMultiplierToleranceBlack0100 Brown11011Red21022Orange3103 Yellow4104 Green51050.5Blue61060.25Violet71071Grey8108 White9109 Gold 10-15Silver 10-210None  20(1) The key to fast recognition is to determine the resistance value within a certain magnitude according to the color of the third band, and then to recognize the resistance of first and second band, following this way, the number can be read out quickly.GoldunitsBlacktensBrownhundredsRedthousandsOrangeten thousandsYellowhundred thousandsGreenmillionsBlueten millions(2) Memorize the number of colors represented by the first and second rings, the following table is the number each color represents.On the order of magnitude, they can be divided into three grades: gold, black, brown is Ω; red, orange, yellow are KΩ; green, blue is MΩ.(3) When the second band is black, the third band is represented by an integer, and a special case at the time of reading needs to be noted, for example, the third band is red, the resistance value is a whole number kΩ.(4) Remember the errors represented by the fourth band color, that is, gold is 5%, silver is 10%, colorless is 20%.Examples(1) When the four-color bands are yellow, orange, red, and gold successively because the third ring is red, the resistance range is several kΩ, according to the representing number of yellow and orange is "4" and "3" respectively, the reading number is 4.3 kΩ, and the fourth band is gold, so the error is 5%.(2) When the four-color bands are brown, black, orange, and gold in turn, because the third band is orange and the second band is black, the resistance range should be tens of kΩ, the brown is representing “1”, so the reading number is 10 kΩ, the fourth band is gold, its error is 5%.2. Chip resistorsChip resistors have the advantages of small size, lightweight, high installation density, high seismic resistance, sound anti-interference ability, and good high-frequency characteristic. It is widely used in computers, mobile phones, electronic dictionaries, medical e-products, video cameras, VCD machines,s, etc.Chip components can be divided into three types according to their shape: rectangular, cylindrical, and special-shaped. There are resistors, capacitors, inductors, transistors, and small integrated circuits. The nominal method of the chip components is different from that of the common components. The following is mainly about the nominal method of chip resistors.The resistance value of a chip resistor is the same as that of a general resistor. There are three methods of nominal resistance, but it is not exactly the same as that of general resistors.1) Digital nominal method (usually for general rectangular chip resistors)This method is using a three-digit number on the resistance body to indicate its resistance. Its first digit and second digit are significant digits, and the third digit represents the numbers of "0" added after the significant number, and this digit place does not appear as a letter.Example: “472′” represents “4700Ω”, “151” represents “150”.If it is a decimal, use "R" to denote "decimal point" and take up an effective digit, and the remaining two digits are valid numbers.Example: “2R4” represents “2.4Ω”, “R15” represents “0.15Ω”.2) Colour bands nominal method (used in general cylindrical fixed resistors)The chip resistor, like general resistors, is usually indicated by four/five/six bands. The first band and second band are significant numbers and the third band is a multiplier.IX. Resistor FunctionSmall power resistors are usually made of carbon film packaged in plastic shells, while high power resistors are usually wire wound resistors, which are made by metal wires with high resistance wrapped on the porcelain core.If the resistance value of a resistor is close to 0Ω, the resistor has not any effect on the current. In parallel with this kind of resistors, the circuit will be short-circuited and the current is infinitely large. If resistance is very large or infinite, the circuit is in series with such a resistor can be regarded as an open circuit, that is, the current is 0A. The commonly used resistor in the industry is between two these extreme cases. In other words, it has a certain resistance and can pass through a certain current, but the current is not as large as in a short circuit. The resistor's current limiting effect is similar to that of a small diameter tube connected to two large-diameter tubes to limit water flow. It is defined as the resistance corresponding to that 1V voltage is added to the conductor to generate 1A current, in fact, the term "resistance" refers to a property, whereas in electronic products, it often refers to a component such as a resistor.FAQ1. How does a resistor work?A resistor is a little package of resistance: wire it into a circuit and you reduce the current by a precise amount. ... A resistor like this is described as wire-wound. The number of copper turns controls the resistance very precisely: the more copper turns, and the thinner the copper, the higher the resistance.2. What are the 4 types of resistors?Resistor types:Fixed resistors.Variable resistors.Thermistors.Varistors.Light dependent resistors.3. What is resistor and its unit?Resistor is an electrical component that reduces the electric current. The resistor's ability to reduce the current is called resistance and is measured in units of ohms (symbol: Ω). If we make an analogy to water flow through pipes, the resistor is a thin pipe that reduces the water flow.4. What is resistor in simple words?A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.5. What is the main function of resistor?A resistor is a passive electrical component with the primary function to limit the flow of electric current.6.How do you identify a resistor?Some resistors have contact plates on the bottom. Read the 3 or 4 numbers on the resistor. The first 2 or 3 represent the significant digits and the last indicates the number of 0s that should follow. For example, a resistor reading 1252 indicates a rating of 12,500 ohms or 1.25 kilo-ohms.7. What is resistor formula?According to Ohm's law, the voltage drop, V, across a resistor when a current flows through it is calculated by using the equation V=IR, where I is current in amps (A) and R is the resistance in ohms (Ω). So the voltage drop across R1 is V1=IR1, across R2 is V2=IR2, and across R3 is V3=IR3.8. What is difference between resistor and resistance?Resistance is the property of a conductor, which determines the quantity of current that passes through it when a potential difference is applied across it. A resistor is a electrical componet with a predetermined electrical resistance, like 1 ohm, 10 ohms 100 ohms 10000 ohms etc.9. What are the 2 types of resistors?The resistors are mainly divided into two types, first Fixed Resistors and second, variable resistors. In Fixed resistors, the electrical resistance of the resistor the remains same while in variable resistor it does change with some physical variable.10. What are the five examples of fixed resistor?The different types of fixed resistors include:Wire wound resistor.Carbon composition resistor.Carbon film resistor.Metal film resistor.Metal oxide film resistor.Metal glaze resistor.Foil resistor.11. What can be used as a resistor?Explained another way: an electrical circuit that has a difference of 2 volts, with 1 Ampere of current flowing through it, has a resistance of 2 Ohms. All electrically conductive materials are somewhat resistive, too. Because of this, even a good electrical conductor, such as metal wire, can be used as a resistor.12. How do you use a resistor in a circuit?Dividing voltage: You can also use resistors to reduce voltage to a level that's appropriate for specific parts of your circuit. For example, suppose your circuit is powered by a 3 V battery but a part of your circuit needs 1.5 V. You could use two resistors of equal value to split this voltage in half, yielding 1.5 V.13. What happens if there is no resistor in a circuit?If there really were no resistance in the circuit, the electrons would go around the circuit, and arrive back at the beginning of the circuit with as much energy as the potential difference (the voltage). That final energy is usually what is dissipated as heat or other types of energy by the circuit.14. How do you connect a resistor?Resistors are said to be connected in “Series”, when they are daisy chained together in a single line. Since all the current flowing through the first resistor has no other way to go it must also pass through the second resistor and the third and so on.15. What is the use of resistor color code?Components and wires are coded with colors to identify their value and function. Resistor Color Coding uses colored bands to quickly identify a resistors resistive value and its percentage of tolerance with the physical size of the resistor indicating its wattage rating.You May Also LikeHow to Distinguish Resistor Color Codes? (Axial Resistors)

  After 20 years, your life may be like this:The electronic skin on your pulse can monitor your heart rate and blood sugar at any time to realize intelligent pulse detection;The electronic skin on your throat can "voice" for the deaf and mute by feeling the pressure changes produced by the movement of the throat muscles;Your whole body may become a network center, and the sensors in your body will connect with the outside world...All this seems very far away, but these technologies are quietly gestating, and are very likely to become disruptors of new technologies.Flexible Electronics: The Future of TECHNow is the era of smart phones, but the current smart electronic products are still rigid electronic devices. In the future, mankind is about to enter a new era, the era of flexible electronics. Flexible electronic devices that are as soft as human skin will be the next development trend of the electronics industry, and may even subvert human life. Catalog I What is Flexible electronics?II Applications of flexible electronics2.1 Flexible electronic display2.2 Thin film solar panels2.3 RFID2.4 Electronic skinIII ConclusionFAQ  I What is Flexible electronics? The concept of flexible electronics started in the 1980s, when people tried to replace inorganic semiconductors such as silicon with organic semiconductors, so that organic electronic devices have flexible characteristics.Flexible electronic technology is a brand-new electronic technology revolution. It is an emerging electronic technology that makes organic and inorganic materials electronic devices on flexible, malleable plastic or thin metal substrates. It has a wide range of fields in information, energy, medical treatment, and national defense.  Applications of flexible electronics In addition to integrating electronic circuits, functional materials, micro-nano manufacturing and other fields of technology, flexible electronic technology also spans industries such as semiconductors, packaging, testing, materials, chemicals, printed circuits, and display panels. Not only that, it can also help the transformation and upgrading of traditional industries, such as plastics, printing, chemicals, and metal materials.By improving its performance and industrial added value, flexible electronics will frequently appear in human life, bringing revolutionary changes to the industrial structure and future life. As technology upgrades, flexible electronics materials research and development and rich application products have emerged.II Applications of flexible electronicsWith the development of flexible electronic technology, various electronic products have emerged. Just as microelectronics technology provides a technology platform for large-scale integrated circuits and computer chip technologies, flexible electronic technology provides a brand-new technological platform for the research and development of new products. 2.1 Flexible electronic displayThe flexible electronic display is a brand-new product developed on the flexible electronic technology platform. Unlike traditional flat-panel displays, such displays can be repeatedly bent and folded, thus bringing great convenience to our lives.For example, all visual materials, including books, newspapers, magazines, and video files, can be presented on this display and can be viewed anytime, anywhere. Although current popular MP4 players and personal digital assistants (PDAs) can meet such use needs, the display screen cannot be bent and folded, and can only be read and viewed in a small screen area. And video, visual effects are greatly constrained. In contrast, flexible electronic displays have unparalleled advantages. They are like newspapers. When they are needed, they are unfolded. When they are used, they are curled or even folded. This guarantees the convenience of portability while giving full consideration to the visual effects.Flexible electronic displaySamples of flexible electronic displays have been successfully developed and it is believed that it will be a long way from entering the market. It is worth mentioning that flexible electronic displays use more lightweight organic materials instead of inorganic materials, so their weight is lighter than traditional displays, and this feature helps to improve their portability. In addition, the use of high molecular organic materials offers possibilities for reducing costs. In addition, the flexible electronic display has the characteristics of a thin thickness, and its thickness can be much smaller than that of the popular liquid crystal display. Therefore, another name of the flexible electronic display is a paper-like electronic display.2.2 Thin film solar panelsThin film solar panel is another specific application of flexible electronics technology. In today's world, energy has become a topic of global concern. China not only faces energy shortages but also faces environmental pollution. As a clean energy source, solar energy can effectively alleviate the contradiction of energy shortage under the premise of zero environmental pollution.As the most common way to use solar energy, solar panels can cover a large area at the lowest cost to effectively use solar energy. At present, thin film amorphous Sili-Con solar panels have been successfully developed and marketed. Thin film solar panel Thin-film solar panels based on flexible electronic technology can meet high-power generation needs, such as the use of thin-film solar panels in solar power plants in sunny desert areas.In addition, it can also make full use of its flexible and lightweight features to integrate it into clothing. Putting on such clothes to walk or exercise in the sun, the power of small appliances (such as MP3 players and laptops) that are carried around can be supplied by the thin-film solar panels on the clothes, thus achieving the purpose of saving and environmental protection.2.3 RFIDRadio frequency identification (RFID) technology can be used to complete information input and processing, fast and convenient operation, and rapid development without manual contact, and is widely used in production, logistics, transportation, medical, food, security and other fields. RFID systems usually consist of transponders and readers.The electronic tag is one of many forms of transponder, and can be understood as a transponder with a thin film structure, which has the characteristics of convenient use, small size, thin and light, and can be embedded in the product. More and more electronic tags will be used in future RFID systems.Flexible Electronics in RFIDIn this response to Covid-19, flexible electronic technology has played a huge role in body temperature measurement.Group body temperature measurement has problems such as huge number of monitoring people, cumbersome temperature measurement work, and difficulty in continuous temperature recording. Wearable temperature measuring stickers made by introducing flexible electronic technology can record and analyze the body temperature data of the target population. In this way, potential threats can be discovered and eliminated through long-term monitoring, thereby helping management departments to achieve personnel management monitoring.2.4 Electronic skinAnother important application of flexible electronics is electronic skin. Electronic skin, also called skin-like electrons, is basically characterized in that various electronic components are integrated on a flexible substrate to form a skin-like circuit board, which has high flexibility and elasticity like skin and can be used in many other applications. electrical equipment.It can be said that the potential of flexible electronic skin is great. With the popularization of technologies such as smart medical care, virtual reality, and artificial intelligence, the demand for wearable devices has surged, and flexible electronic skin is a perfect combination of wearable devices. Think about an electronic component installed on the body and used as a skin, isn't it sci-fi?Electronic skinIII Conclusion Folding computers, folding mobile phones, and wearable digital products are in the ascendant. With the development of science and technology, flexible electronic devices have received more and more attention from the society. Such devices can still work under bending, folding, twisting, compression or stretching conditions. In the future, flexible electronic equipment will have a very broad development space in the fields of energy, medical, information and communication.Pieces of work brought by flexible electronics are interpreting the integration of innovation and tradition in the era of the Internet of Everything, and the era of science and technology connecting everything is approaching.You can boldly imagine that in 20 years, your life might be like this:In the morning, the flexible electronic skin watch on your body wakes you up and reports the quality of your sleep. Put on your glasses, and the day’s schedule has been displayed for you on the transparent screen. After washing, the robot has prepared breakfast for you and your family; After going out, the smart watch on your wrist shows that the air quality is excellent; the smart assistant called "Flying" for you and has parked outside the house, waiting for you to start your day's itinerary... FAQ 1. Why are electronics flexible?The key advantages of flexible electronics, compared with current silicon technologies, are low-cost manufacturing (e.g. ink-jet printing and roll-to-roll imprinting) and inexpensive flexible substrates (e.g. plastics). ... In principle, flexible electronics is ideal for integration. 2. Where are flexible electronics used?Consumer electronics devices make use of flexible circuits in cameras, personal entertainment devices, calculators, or exercise monitors. Flexible circuits are found in industrial and medical devices where many interconnections are required in a compact package. 3. How could Flexible Electronics benefit the consumer?Among the benefits of flexible electronics (compared to traditional, rigid alternatives) are size, weight, portability, and energy efficiency. Above all, they make previously impossible designs and technologies (such as wearable devices) possible. 4. When was flexible electronics invented?1960s. Flexible electronics have a long history. The first flexible device was made in the 1960s by thinning crystalline silicon solar cells for use in extraterrestrial satellites. Today, smart credit cards carry bendable microchips which are made using stretchable Silicon. 5. What are flexible electronics made of?Flexible Electronics: generally refers to a class of electronic devices built on conformable or stretchable substrates, usually plastic, but also metal foil, paper and flex glass. 6. What are the two major approaches of making flexible electronics?(1) Transfer and bonding of completed circuits to a flexible substrate(2) Fabrication of the circuits directly on the flexible substrate  7. What makes flexible electronic display attractive?One property of flexible electronics which deserves to be highlighted is their robustness. This makes a great difference for applications such as wearables, notebooks and other consumer electronics which traditionally feature glass-based displays or sensors. 8. How flexible electronics are made?Compared with conventional microelectronics, flexible electronics does not require extrinsic packages such as ceramics. Instead, flexible circuits and packages can be manufactured and integrated together using only plastics. ... These layers can then be stacked together to complete the flexible electronic systems. 9. Why are flexible electronics important?Among the benefits of flexible electronics (compared to traditional, rigid alternatives) are size, weight, portability, and energy efficiency. Above all, they make previously impossible designs and technologies (such as wearable devices) possible. 10. Why do we need flexible materials?Not only does flexible packaging use less material than its rigid counterparts, leading to a lower overall packaging cost, it also creates less waste. Fres-co states that flexible packaging formats create 50 percent less waste than rigid ones, while also reducing greenhouse gas emissions and BTU consumption. 

In addition to magnetic element design, feedback network design is also the least known and very troublesome work of switching power supply. It involves analog electronic technology, control theory, measurement and computing technology and other related issues.CatalogI Frequency response1.1 Basic concept1.2 Frequency response of basic circuits1. 3 Characteristics of LC filter circuitII Time-domain response of basic circuits2.1 Step-function signal2. 2 Step response of single time constant2. 3 Step response of LC circuitIII PluralIV Complex functionV Exchange C and LThe purpose of switching power supply loop design is to achieve the required output (voltage or current) accuracy within the range of input voltage and load variation, and meanwhile, makes equipment to work stably under any circumstances. What’s more, achieve fast response and small overshoot when load or input voltage changes. At the same time, it can reduce the low frequency pulsation component and the switch ripple and so on.To better understand the feedback design method, the basic knowledge of frequency characteristics, negative feedback and operational amplifier in analog circuits is reviewed importantly. Here the basic design method of feedback compensation is discussed with the example of forward converter. It also introduces how to test the open loop response by using analyzer HP3562A, and then design and correct the network according to the test characteristics and verify the design results. Finally, introduce the simulation test.I Frequency responseIn electronic circuits, reactance (inductor and capacitor) elements are inevitable. For different frequencies, their impedance varies with frequency. Their electrical signals not only change in amplitude, but also in phase. The relation between output and input of sinusoidal signals with different frequencies is called frequency response.1.1 Basic conceptThe output-to-input ratio of the circuit is called a transfer function or gain. The relation between the transfer function and the frequency, that is, the frequency response can be represented by the following expression: G=(f)∠φ(f), while G(f) is the relation between the modulus (amplitude) of the transfer function and the frequency, which is called the amplitude-frequency response; ∠φ(f) is the relation between the phase difference of the output signal and the input signal and frequency, which is called the phase frequency response.The typical logarithmic amplitude-frequency response is shown in Fig. 1, and Fig. 1 (a) is the amplitude-frequency characteristic. It is drawn on the logarithmic coordinate with logarithmic frequency f as the transverse coordinate, and the longitudinal axis gain is represented by 20logG(f). Fig. 1 (b) is the phase frequency characteristic, and the vertical axis represents the phase angle φ on the single logarithmic coordinate with logarithmic frequency f as the transverse coordinate. This diagram is called Potier graphs.Fig. 1 Potier graphsIn terms of amplitude-frequency characteristics, there is a frequency range in which the gain is basically constant, and when the frequency is higher or below than a certain frequency, the gain will decrease. When the high frequency increases, if the gain is lower than the constant part of the 3dB, the frequency is called the upper limit frequency or the upper limit cut off frequency, representing by fH, while the frequency is larger than the cut-off frequency is called the high frequency region. At low frequency, when the gain is lower than the constant part of 3dB, the frequency is called the lower frequency or the lower rate limit, representing by fL, where the frequency is lower than the lower cut-off frequency is called the low frequency region. Between the high-frequency cut-off frequency and the low-frequency cut-off frequency is called the intermediate frequency region. In this area, The gain is basically unchanged. The definition of it: BW=fH-fL1.2 Frequency response of basic circuits1.2.1 High frequency responseFig. 2 High - frequency responseIn the high-frequency region, the circuit that affects the high-frequency response of the system (circuit) is shown in Fig. 2. Taking Fig. 2(a) as an example, the ratio of output voltage to input voltage decreases with the increase of frequency, and meanwhile the phase lags.Using complex variables to obtainAs for the actual frequency, s=jw=j2πf , making(F-0)The high-frequency voltage gain of the circuit can be obtained: The relationship between the frequency and phase angle, and the mode (amplitude) of the gain in the high frequency region are obtained:The logarithmic amplitude-frequency is(F-1)1.2.1 Amplitude-frequency response1) when f<<fH,The gain value is 1, a horizontal line at the horizontal coordinates;2) when f>>fH,It can be seen that for the logarithmic frequency coordinate, the upper formula can be represented by an oblique line, the slope is -20dB/ tenth frequency (- 20dB/dec), and intersects with the 0dB line at f=fH, so fH is called turning frequency. When f=fH, that is  , the high frequency response takes the 0dB line and-20dB/dec as the asymptote, and the maximum difference at the turning frequency is-3dB. The amplitude-frequency characteristic is shown in Fig. 3(a)Fig. 3 High - frequency potier diagramWhen the frequency is equal to the turning frequency, the capacitor reactance is exactly equal to the resistance. When the frequency increases continuously, the impedance of capacitor C decreases by-20dB/dec, that is, the frequency increases by 10 times and the capacitive reactance decreases by 10 times, so the output attenuates with-20dB.1.2.2 Phase-frequency characteristic The relationship between phase and frequency can be made in the following ways according to formula (F-2).- When f<<fH, φ closes to 0 ° , getting a straight line.- When f>>fH, φ closes to 90 ° , getting a straight line.- When f=fH, φ=45 °.- When f=0.1fH, and f=10fH, φH is -5.7 °and -84.3 °respectively, so the slope is represented approximately by 45/dec oblique line. The phase frequency characteristics are shown in the following figure.Fig. 3 High - frequency potier diagramFrom the amplitude-frequency and phase-frequency, it can be seen that when the frequency increases, the gain of the circuit becomes smaller and the phase lag becomes larger. When the phase reaches 90 °, the gain is 0. Both amplitude-frequency and phase-frequency characteristics are determined by upper frequency fH. It can be seen from formula (F-0) that the upper cut-off frequency is determined by the time constant (RC) of the circuit. If the time constant L /R of Fig. 2(b) is equal to the time constant RC of Fig. 2(a), the porter diagram of Fig. 2(b) circuit is exactly the same as that of Fig. 2(a).As can be seen from Fig. 3, the high frequency signal attenuates greatly, while the low frequency signal is preserved. Therefore, this circuit is also called a low-pass filter. For Fig. 2(a) circuits, if the time constant is much larger for the time studied, that is, the resistance and capacitance values are large  Uo=Uc，From  it can get This is an integrator. It can be seen that the same circuit has different functions for different research purposes.1.2.3 Low Frequency CharacteristicWe study the characteristics of the two circuits in the low frequency region shown in Fig. 4. Fig. 4 Low -frequency regionUsing the complex variables, from Fig. 5 (a), Fig. 5 Low - frequency potier diagramwe can getAccording to actual frequency and s=jw, makingGettingThus the gain (mode) and phase angle of the low frequency region of the circuit are respectively:Use the linear approximation method which is similar to the high frequency response, the potier diagram of the low frequency response can be drawn, as shown in Fig. 5. The fH in the diagram is the lower limit frequency, that is, the low turning frequency. Below the turning frequency, the gain of the circuit decreases with the decrease of the frequency, and the characteristic slope is 20dB/dec. When the phase reduces with the frequency, using the forward input phase. Maximum advance 90 °, gain 0 (- ∞, dB).The lower limit transition frequency is also related to the circuit time constant RC (L/R). If the time constants of Fig.4 (a) and Fig.4 (b) are the same, their potier graphs are identical.It can also be seen from Fig.5 that the circuit attenuates the low frequency signal, while the high frequency signal passes smoothly due to the reduction of capacitance. So this circuit is also called a high-pass filter. For Fig. 4(a), when the time constant of the Fig. 4(a) circuit is much smaller than the time interval we studied, the output obtains the variable input signal, then the circuit is a differential circuit.1. 3 Characteristics of LC filter circuitFig. 6 Frequency characteristic of LC filter circuitIn the switching power supply, the forward output filter (Fig. 6) is a LC network with a load resistor in parallel with the output capacitor, and the load resistor can be changed from a certain value (full load) to infinity (no load). For Fig. 6, we can also use complex variables to getAccording to actual frequency and s=jw, makingGetting (F-2)The characteristic impedance of the circuit is, at small range of f close to f0,, making , so The gain amplitude-frequency and phase-frequency characteristics are as follows respectively:(F-3)The Potier diagram of the LC filtering circuit can be made by the expressions (F-3), as shown in Fig.. When f <f0, the formula (F-3) tends to 1, that is 0db, φ≈ 0°; When f >f 0, the second term in the denominator (F-2) is much larger than the other two, the inductive reactance is increased by 20dB/dec, the capacitive reactance by 20dB/dec is decreased, the load impedance is far greater than the capacitive reactance, and the amplitude-frequency is decreased by 40dB/dec, φ tends to -180 °. When f is close to f0, different D values and amplitudes do not increase. The greater D value is equivalent to the light load, that is circuit underdamping, the higher the amplitude. With the increase of the load, the equivalent load resistance decreases, the D value decreases, and the peak value of lifting decreases. When D=1, at critical damping, amplitude-frequency increases slightly from low frequency to f0, at f=f0, it returns to 0dB, and when f >f0, the gain tends to -40dB/dec. When D < 1, the damping is equivalent to full load or overload. In the vicinity of f →f0, the amplitude doesn’t raise, but also attenuates with the increase of frequency, and the slope of attenuation is about 20 times of f0. The relationship between phase shift and f/fc and different D values is shown in the Fig. 8 of amplitude-frequency reaching-40dB/dec. It can be seen that the phase difference between the output and the input is 90 °at the turning frequency point f 0, regardless of the D value. For the high underdamped filter (Ro > 5Zo), the phase frequency characteristic changes rapidly with the frequency. For Ro=5Zo, when frequency at 1.5f0, the phase shift is almost 170 °. But in the circuit with gain slope of-20dB/dec, it is impossible to produce phase shift greater than 90 °, and the phase frequency characteristic changes with the frequency. The change rate of phase shift of in Fig. 8 is much lower than that of -90 °/dec in Fig. 8.Fig. 7 Frequency amplitude of LC filter circuitFig. 8 Phase frequency of LC filter circuitIf the output capacitance in Fig. 7. has ESR , is equivalent series resistor Resr. It is generally very small and the low frequency characteristic will not be affected by 1/ωC<<Resr, in low frequency band. When the frequency increases to At this time  ,the phase is raised by 45°. As the frequency continues to rise, the output filter circuit becomes a LResr circuit. The LC filter attenuates from-40dB/dec to-20dB/dec after the frequency fesr, and the phase shift tends to lag by 90 ° instead of 180 °. This means that the capacitance of the ESR provides a zero point.II Time-domain response of basic circuitsThe circuit analysis includes steady state analysis and transient analysis. The frequency response of the amplitude and phase of the circuit is analyzed with sine wave as the basic signal, which is the steady-state response. This method is called frequency domain analysis method.Another method of circuit analysis is transient analysis. The step-function signal is used as input signal to study the variation of circuit output with time, which is called step response. It is judged by the rising time of the waveform and the flat-top drop size. It's called time domain analysis.2.1 Step-function signalThe graph represents a step voltage that can be represented as:It can be seen that the change rate of step signal waveform is infinite, but it is a constant during the conversion. From the point of view of frequency analysis, the extremely fast rate of change includes harmonic components from DC to very high frequency. Whether the output of the circuit can repeat the waveform of the input signal: the rising time of the output reflects the high frequency response of the circuit, while the flat top drop reflects the low frequency response of the circuit.2. 2 Step response of single time constantLet's study the step response of Fig. circuit. The step response is represented by the rise time tr and the flat-top landing δ. Fig. 9 Step response of single time constantRise time trWhen the step signal is added to the input of Fig. (a) circuit, according to the general law of RC circuitU0-initial value;  U∞-terminal value; τ= RC- time constant. The capacitance initial voltage U0  is zero.In the formula τ = L/R, Ui is the voltage value of the flat top part of the step signal. The relation between Uo/Ui  and time is shown in Fig. 10. The three elements of RC circuit: initial value, final value and time constant. The input rises to the final value in a very short time, and the output voltage changes with time exponentially, which takes a period of time to reach the final value. This phenomenon is called frontier distortion. The interval between 10% of the output end value and 90% of the final value is generally defined as the rising time tr.Fig. 10 The relation between Uo/Ui and tAs can be seen from the expressions (6-18), when t=t1according to the same principle, when t＝t2Because ofSo the rise timeHigh frequency response of circuit f 1/(2πRC)H，gettingTherefore, the rise time is inversely proportional to the upper bound frequency. The higher the is, the smaller the rise time tr is and the lower the front distortion is. For example, the bandwidth of a circuit is 1MHz, and the step-up time is tr=0.35 rt μs. We use Fig. (a) to study flat-top landing. When step input, the output isThe relationship between and time is shown in Fig. 11. If the time tp is small than τ, the output voltage will still decrease according to the exponential law, though the input voltage is invariable, and the decreasing speed is related to the time constant. This phenomenon is called flat-top descent. Fig. 11 Flat-top descentBecause of tp < τ, it can be approximately obtained:Considering that fL=1/ (2πRC), then getsIt can be seen that the flat-top drop δ is proportional to the lower limit frequency fL, and the lower the fL , the smaller the flat-top fall. In switching power supply, the sudden change of load and input power supply voltage is also a step-by-step response. In the above research, the system is still in the linear state, but in the switching power supply, there are high gain amplifiers, under the action of the step signal, the system usually enters the nonlinear state, the large signal response is often lower than the small ones.2. 3 Step response of LC circuitFig. 12 Step response of LC circuitThe LC circuit is shown in Fig. 12. If the circuit loss resistance is zero,  initial voltage of the inductance initial current and capacitance are zero, under the action of step-up signal, getting the formulas are as follows:Ui as step input signal; resonant angular frequency of LC circuitCharacteristic Impedance of resonant CircuitThe peak value of inductance current isDifferent initial values, excitation and circuit conditions, initial and final values of the waveform amplitude are different, but the phase relationship is fixed.Note: plural conceptIII PluralThe complex number is composed of real part and imaginary part, that is,, gettingSince a complex number is composed of two numbers, we can use the x axis as the real number and the y axis as the imaginary axis, as shown in Fig 13. Redraw the Fig. 13 as Fig. 14, and you can see that the complex number can be expressed in two quantities: one is the distance to the coordinates (0,0) , and the other is the angle  from the counterclockwise to the point . The value r is called the modulus of the complex number, and the angle φ is called the amplitude angle of the complex number.Fig. 13 Complex graphic methodFig. 14 Expressing complex number by distance and angleIn electricity, we naturally think of using complex numbers to express values and phases. For example, if you represent a sinusoidal quantity of electricity, the sine is projected on the imaginary axis with the coordinate distance, and the cosine is projected on the real axis, so a complex number can also be represented as (F-4)According to Euler's formula The upper form can be solved as  (F-5), or simplified to (F-6)It can be seen that a complex number can be expressed in the following ways: (F-4) is a complex cartesian coordination, (F-5) is exponential, and (F-6) is polar coordinate. The three can be converted to each other. The complex number can be added or subtracted by cartesian coordination, and the multiplication and division operations by the exponential or the polar coordinates.According to the above mentioned formulas, if φ==90°, soAny phasor multiplied by j, phase rotation 90°: + represents counterclockwise rotation; - represents clockwise rotation. If the virtual axis is j, times j, then rotates to the solid axis to change to -1, then , so is the imaginary unit.IV Complex functionThe instantaneous amplitude and phase can be expressed by a complex number. If a sinusoidal quantity is expressed, the complex number in the circuit is frequency dependent. There are two aspects of interest in steady-state design: what are the parameters of a function that are zero? And where is the function infinite? These two cases represent the zeros and poles of the function respectively.For example It is obvious that x=2 in this function while phase is zero, that is, the complex amplitude is 2, the phase is 0, in other words, the real part is 2, and the imaginary part is 0 (Fig. 15), and the x=3 function becomes infinite. Its complex image value 3 and phase value 0 as another example, we can see that the capacitance has frequency dependent complex 1/sC (s as an complex variable, frequency-dependent), while the inductance is sL. Fig. 15 shows the switching power output filter (capacitor has ESR, inductor has coil resistance, not considered here). Form a voltage divider with an output to input ratio of Fig. 15 Complex impedance of inductor and capacitorThis function will not be zero, but when, that is, there are two poles. The two poles appear at the resonant frequency point and the phase angles are 90 °and 270 °(pure imaginary number, no real part, as shown in Fig. 16 ). Of course, the physical meaning here is that the LC network resonates at this frequency and the output is amplified infinitely at this frequency. In fact, there is always resistance in the actual circuit, so the magnification is not infinite, that is, the two poles are not on the virtual axis and the real part is not zero.Fig. 16 Poles of LC resonant frequencyV Exchange C and LFor capacitive currentIf Us=Uest，the voltage is a sine wave [because of ]，we can getGetting the resistance is: In the definition of Laplace transformation, we do not have to actually solve the integral because the integral is implicit in solving the differential equation. Similarly, we can get the inductance impedance: Similarly, use  to replace  to get: So the resistance is Z=sL

In this article, we will provide you the basic introduction to FPGA and ASIC, illustrate their differences in the design, and many other complement content. CatalogI. What is FPGA?II. What is ASIC?III. What is the Difference Between FPGA and ASIC?      3.1 Difference in RTL Design      3.2 Difference in Development ProcessIV. Difference SummaryFAQI. What is FPGA?The circuit design with hardware description language (Verilog or VHDL), which can be easily synthesized and distributed, can be quickly made to FPGA for testing. It is the mainstream of modern IC design verification technology. These editable elements can be used to implement basic logic gates (such as AND, OR, XOR, NOT) or more complex combinatorial functions such as decoders or mathematical equations. In most FPGA, these editable components also contain memory elements such as triggers (Flip-flop) or other more complete memory blocks.System designers can connect blocks of logic inside FPGA via editable connections as needed as if a circuit test board had been placed in a chip. The logic blocks and connections of a finished FPGA can be changed according to the designer, so FPGA can meet the required logic functions.The speed of FPGA is generally slower than that of ASIC, and the area of realizing the same function is larger than that of ASIC. But they also have many advantages, such as quick production, modification to correct errors in the program, and cheaper costs. Vendors may also offer cheap but poorly edited FPGA. Because these chips have poor editable capabilities, the development of these designs is done on an ordinary FPGA, and then the design is transferred to a chip similar to ASIC. Another way is to use CPLD (Complex Programmable Logic Device). Learn the basics of what is an FPGA. This video discusses the history of FPGAs and how they have advanced over time. It discusses some applications that are possible. Finally it will introduce the two languages used to program FPGAs: VHDL and Verilog.  FPGA StateFPGA (Field Programmable Gate Array) is the product of further development on the basis of PAL, GAL, CPLD, and other programmable devices. As a semi-custom circuit in the field of ASIC, it not only solves the deficiency of custom circuits but also overcomes the shortcoming of the limit of the gate of the original programmable device, that is, FPGA allows unlimited programming. FPGA Parts ExplainationFPGA adopts the concept of LCA (Logic Cell Array), which includes three parts: configurable logic module (CLB), Input-Output Block(IOB), and Interconnect. FPGA is a programmable device with different structures compared with traditional logic circuits and gate arrays (such as PAL, GAL, and CPLD devices). FPGA uses a small lookup table (16×1RAM) to implement combinatorial logic. Each lookup table is connected to the input of a D-trigger, which drives other logic circuits or drives the I / O. Therefore, the basic logic unit module can realize both combinational logic function and sequential logic function. These logic units connect with mental wires or I/O contracts. In addition, the logic of FPGA is to load programming data into internal static storage units. The value stored in the memory cell determines the logical function of the logical unit and the connection between modules or between modules and I / O contracts and ultimately determines what FPGA can achieve.II. What is ASIC?An application-specific integrated circuit(ASIC) is a microchip designed for a special application, such as a special kind of transmission protocol or a hand-held computer. People might contrast it with general integrated circuits, such as the microprocessor and the random access memory chips in PCs. ASIC is used in a wide range of applications, including auto emission control, environmental monitoring, and personal digital assistants (PDAs).Mining was for a long time a GPU only game, but with ASIC miners seemingly everywhere these days, are they actually profitable? ASIC StateAt present, ASIC is considered to be a kind of integrated circuit designed for special purposes in the field of integrated circuits. An integrated circuit is designed and manufactured at the requirement of a specific user or a particular electronic system. That is, the ASIC is characterized by a request for a specific user. The ASIC is smaller in volume and lower in power consumption than that of a general integrated circuit in mass production, also has the advantages of improved reliability, improved performance, enhanced confidentiality, lower cost, and so on. Full Customization and Semi-customizationASIC is divided into full customization and semi-customization, so an ASIC can be pre-manufactured for a special application or it can be customized (typically using components from a "building block" library of components) for a particular requirement of customers.Full customization design requires designers to complete the design of all circuits, so it requires a lot of manpower and material resources, although it has good flexibility the development efficiency is low. If the design is ideal, full customization can run faster than semi-custom ASIC chips. When using the standard cell, the semi-custom can select SSI (gate), MSI (such as adder, comparator, etc.), data path (such as ALU, memory, bus, etc.),. memory and even system-level modules (e.g. multipliers, microcontrollers, etc.) ) and the IP core from the standard logic unit library. When these logic units have been laid out and designed reliably, the designer can easily complete the system design. Modern ASIC often contains a 32-bit processor, storage units like ROM, RAM, EEPROM, Flash, and other modules. Such ASIC is often called SoC(system in the chip).ASIC DevelopmentProgrammable ASIC is another characteristic branch of ASIC development. It mainly uses programmable integrated circuits such as PROM, GAL, PLD, CPLD, FPGA, or logic array to get ASIC. Its main feature is to provide software design and programming directly, completes the function of ASIC circuit, and it does not need to be processed by IC process line.There are many kinds of ASIC designs for programmable devices, which can meet different requirements. PLD and FPGA are commonly used programmable devices. It is suitable for the design of digital circuits with a short development cycle, certain complexity, and circuit scale, especially for electronic system design engineers using EDA tools for ASIC design.III. What is the Difference Between FPGA and ASIC? 3.1 Difference in RTL DesignThere are many differences between FPGA and ASIC. The logic of ASIC is usually much larger than that of FPGA. There is an order of magnitude difference in gate numbers, and the running clock is much higher than FPGA. Moreover, FPGA is relatively flexible than ASIC because it can be programmed, but only in terms of RTL design: (1) ASIC tends to be more conservative, any changes to logic needed careful consideration, and make alternative choices in case of a correction. Any modification to RTL is almost incremental, and even if the previous logic is wrong, it will not be deleted, but one more branch is made.(2) ASIC has higher requirements for coding style. Coding style requirements for all modules are consistent, thus favoring the fault check.(3) ASIC design pays more attention to the clock and reset. In particular, clocks are critical to the design of ASIC, and reset is critical to BIST testing. ASIC uses libraries to design in this respect. ASIC usually does not use a counter to divide frequencies, which can lead to unclean clocks. Unless it's a very low-frequency clock, ASIC is also much more cautious about signal processing across clock domains. The closing and opening of the clock also need to be strictly checked.(4) ASIC has to consider the problems of SCAN testing and BIST, so it is necessary to do BIST insertion for SRAM when designing and to reserve interfaces for SCAN. Although most of the interfaces are done by tools, RTL authors often have to do some top-level complex work manually, logic such as the source of the SCAN clock.(5) FPGA often uses existing IP, it needs to consider the balance of resources because there is a problem of resource waste in FPGA. ASIC rarely needed to consider this problem, the main consideration of it is its performance and power consumption, except SRAM and CLK which is related to reset in logic choice, the other are handwritten. So the logic is basically no waste, and more compact.(6) ASIC timing is more predictable and adjustable, so it can write a lot of logic. 3.2 Difference in Development ProcessThe differences between FPGA and ASIC development processes: ASIC and FPGA Design Flow ASIC and FPGA Implementation StepsThe first step is to implement functionality in a way that is generally described in HDL, such as Verilog, VHDL. Of course, small-scale circuits can also use circuit diagram input mode.The second step is to ensure the correctness of circuit functions, also known as verification. It can be realized by software simulation, hardware simulation, and so on. Software simulation is generally intuitive and easy to debug because the state of every moment can be seen, this is like debugging software programs. Hardware simulation generally refers to FPGA verification, that is, the circuit is implemented with FPGA, and then run it. The advantage of this is that it is very fast. For example, a video decoding core is used to solve a frame of the image, and software simulation can even use the best server, it still takes a lot of seconds to run, but in FPGA, it basically needs milliseconds. For a large mode verification of the circuit, is essential.The first two steps for digital IP,  the ASIC and FPGA are basically the same, unless some implementation techniques are different.The third step is, once the correctness of the circuit you describe is ensured, to implement it by turning the code you write into a real circuit, such as a register or a NAND gate, which is called synthesis. Because the circuit is becoming more and more complex, the most basic circuit is made into cells, such as register, and non-gate, so it will not be refined to the problem of how to use triode. The difference of this step is the smallest unit of the FPGA and the ASIC. FPGA is a well-made circuit, generally considering universality and efficiency, so the basic circuit unit is relatively large, such as LUT, consist of a register and NAND gate, although it uses one gate, it will take up such a unit. For ASIC, the two-input NAND gate is a simple gate circuit, even in order to distinguish the driveability and the timing characteristic difference, there are several grades, some area is small, some driveability is strong. In general, this step is to make sure your description turned into a library-based circuit description.The fourth step is, when you get a description of the circuit based on the library, you have to consider how these units are placed, which is called layout and wiring. The wiring resources of FPGA are limited, so you need to constantly adjust it to ensure the timing requirements. Map your circuit to the middle of its fixed resource map. ASIC's words are generally based on peripheral circuit requirements, timing requirements, your circuit to a certain location on the chip. After the arrangement, we have to consider whether the connection can pass, whether the delay at all levels can meet the circuit establishing and maintaining time requirements, and so on.The fifth step is output. FPGA is to output a configuration file to make the FPGA chip configure its circuit so that it can achieve the desired function. This file can be downloaded by PC after FPGA power-up, or stored in Flash, when the circuit is powered on, the automatic configuration will make. ASIC is to output a layout file to tell the manufacturer how to corrode silicon chip, how to connect metal, and so on.The sixth step is cost. ASIC has a great advantage in terms of recurring costs with less material is wasted due to the fixed number of transistors in the design. As for FPGAs, a certain number of transistor elements are always wasted although these packages are standard. This means that the cost of an FPGA is often much higher than that of an ASIC. Although the recurring cost of an ASIC is quite low, its non-recurring cost is relatively high. Although it is non-recurring, its value per IC decreases with increased volume.  A Field Programmable Gate Array can be seen as the prototyping stage of Application Specific Integrated Circuits: ASIC is very expensive to manufacture, and once it's made there is no going back (as the most expensive fixed cost is the masks [sort of manufacturing "stencil"] and their development). FPGA can reprogrammable many times, however because of the fact that a generic array of gates is connected to accomplish your goal, it is not optimized like ASIC. Also, FPGAs are natively dynamic devices in that if you power it off, you lose not only the current state but also your configuration. Boards now exist though that add a FLASH chip and/or a microcontroller to load the configuration at startup so this tends to be a less important argument. Both ASIC and FPGA can be configured with Hardware Description Languages, and sometimes FPGA is used for the end product. But generally, ASIC kicks in when the design is fixed.If you analyze the cost of production in relation to the volume, you would find that as you go lower in production numbers, using FPGA actually becomes cheaper than using ASIC.There are, of course, various auxiliary steps in the process. In general, it's all about making sure that the circuits you design are correct and implemented correctly.IV. Difference Summary FPGAASICReconfigurable circuitOne-time circuitDesign mainly with hardware description languages (HDL)Similar to the FPGAFPGA is relatively flexibleASIC tends to be more conservativeFPGA is not strict with the coding because of its programming featureASIC has higher requirements for coding styleFPGA uses small LUT to combine logic configurationASIC design pays more attention to clock and resetFPGA designers generally do not need to care for back-end designThe problems of SCAN testing and BISTFPGA uses existing IPperformance and power consumptionAnalog designs are not possible with FPGAASIC can have complete analog circuitThe speed is generally slowerRun fast than FPGAAllow unlimited programmingAn integrated circuit for a special purposeMore power consumptionMuch more power efficient than FPGA Visual Comparsion(√ means better to select)FPGAASICNRE√Performance√Design Flow√Barrier to entry√Time to market√Analog Blocks√Unit size√Power consumption√Cost per unit√FAQ 1. How do FPGAs work?In general terms, FPGAs are programmable silicon chips with a collection of programmable logic blocks surrounded by Input/Output blocks that are put together through programmable interconnect resources to become any kind of digital circuit or system. ... Unlike processors, FPGAs are truly parallel in nature. 2. What is FPGA and why it is used?FPGAs are particularly useful for prototyping application-specific integrated circuits (ASICs) or processors. An FPGA can be reprogrammed until the ASIC or processor design is final and bug-free and the actual manufacturing of the final ASIC begins. Intel itself uses FPGAs to prototype new chips.3. What is the function of FPGA?The field-programmable gate array (FPGA) is an integrated circuit that consists of internal hardware blocks with user-programmable interconnects to customize operation for a specific application.4. Is FPGA faster than GPU?Compared with GPUs, FPGAs can deliver superior performance in deep learning applications where low latency is critical. FPGAs can be fine-tuned to balance power efficiency with performance requirements.5. Is Raspberry Pi a FPGA?The main difference between the Snickerdoodle and other single-board systems like the popular Arduino and Raspberry Pi products is the inclusion of a Field Programmable Gate Array (FPGA). 6. Does FPGA have memory?The FPGA fabric includes embedded memory elements that can be used as random-access memory (RAM), read-only memory (ROM), or shift registers. These elements are block RAMs (BRAMs), LUTs, and shift registers. ... The data of the ROM is written as part of the FPGA configuration and cannot be modified in any way.7. Is FPGA a microprocessor?Microprocessor vs FPGA: A microprocessor is a simplified CPU or Central Processing Unit. ... An FPGA doesn't have any hardwired logic blocks because that would defeat the field programmable aspect of it. An FPGA is laid out like a net with each junction containing a switch that the user can make or break.8. What is FPGA and ASIC?ASIC stands for Application Specific Integrated Circuit. ... The difference in case of ASIC is that the resultant circuit is permanently drawn into silicon whereas in FPGAs the circuit is made by connecting a number of configurable blocks.9. Is FPGA better than ASIC?In general, we can say that for lower volumes' designs, FPGA flexibility allows to save costs and obtain better results; while ASICs chips are more efficient and cost effective on high volume applications.10. Which one is faster ASIC or FPGA?A single unit of an FPGA chip will be relatively larger than an ASIC chip unit. Because FPGA has its internal structure and a certain size that cannot be changed – while ASIC consists of exactly the amount of gates required for the desired application. FPGA boasts a faster time to market than ASIC.11. What are the main differences between ASIC and FPGAs?Performance and Efficiency. ASICs offer superior performance and are more efficient than FPGAs. Factors like faster speed and the ability to layer multiple functionalities onto a single chip make ASICs outperforms FPGAs. 12. Why do we need FPGA?Why Use an FPGA? ... FPGAs are particularly useful for prototyping application-specific integrated circuits (ASICs) or processors. An FPGA can be reprogrammed until the ASIC or processor design is final and bug-free and the actual manufacturing of the final ASIC begins. Intel itself uses FPGAs to prototype new chips.13. Is ASIC a CPU?CPUs and microprocessors are the same thing. ASIC is just a general term for a microchip. CPUs are technically ASICs, but much simpler devices can be implemented on an ASIC too.14. What is the most preferred FPGA variant?Verilog is currently the most popular. Verilog creates a level of abstraction to hide away the details of its implementation. Verilog has a C-like syntax, unlike VHDL.15. What is ASIC technology?An application-specific integrated circuit (ASIC /ˈeɪsɪk/) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use. ... ASIC chips are typically fabricated using metal-oxide-semiconductor (MOS) technology, as MOS integrated circuit chips. 16. When should ASIC and FPGA devices be used?If your application requires constant bug fixes, feature and design changes, and software flexibility, then FPGAs may be the right solution. If your end application requires high performance, smaller device footprint, and significantly lower power consumption, then ASICs are your best bet. 17. How does an ASIC work?ASICs allow miners to use hardware made specifically for Bitcoin or other SHA-256 algo coins. An ASIC has benefits over CPU, GPU and FPGAs due to being designed for one specific task. They are able to mine Bitcoin at a higher hash rate (speed of processing transactions) than CPUs, GPUs and FPGAs.18. Why use an FPGA instead of a CPU or GPU?This is where FPGAs are much better than CPUs (or GPUs, which have to communicate via the CPU). With an FPGA it is feasible to get a latency around or below 1 microsecond, whereas with a CPU a latency smaller than 50 microseconds is already very good. Moreover, the latency of an FPGA is much more deterministic. 19. Why is ASIC needed?ASICs are designed specifically for one client to provide a function required by the client's end product. For example, a cell phone company may design an ASIC to combine the display backlight controller with the battery charging circuit into a single IC in order to make the phone smaller.20. What is better ASIC or GPU?In short: ASICs are best for mining Bitcoin, Litecoin, Dash, and coins that are based off these algorithms. GPUs are best for mining Ethereum, Monero, Ravencoin, and coins based off those algorithms. Note: Over time all of these coins will produce less thanks to halvings which cut the reward for mining blocks in half.You May Also LikeDiscussion on the influencing factors of clock in FPGA designNew SoM Combination Design Based on Processor and FPGA: FPGA and Processo

IntroductionThe audio power amplifier is a device used to drive the speaker to produce sound, thereby reproducing the sound. It is used in all electronic products that produce sound, which amplifies the smaller audio signal, increases its power, and then outputs it. Pre-amplification mainly used for small signals, and amplifies the voltage of the input audio small signals by using a non-inverting amplifier circuit to obtain the input required by the latter stage. The latter stage mainly amplifies the power so that it can drive the resistor to obtain the required audio.Making an Audio Power AmplifierCatalogIntroductionⅠ What is Power Amplifier Distortion?Ⅱ Types of Audio Power Amp Distortion2.1 Harmonic Distortion (THD)2.2 Intermodulation Distortion (IMD)2.3 Transient Distortion 2.4 AC Interface DistortionⅢ ConclusionⅣ FAQⅠ What is Power Amplifier Distortion?Distortion is the phenomenon that the input signal and the output signal change in the amplitude proportional relationship, phase relationship and waveform shape. The distortion of audio power amplifiers is divided into electrical distortion and acoustic distortion. The former is caused by the circuit, and the latter is caused by the speaker of the sound reproduction device. The types of electrical distortion are: harmonic distortion, intermodulation distortion, and transient distortion. The acoustic distortion is mainly the distortion of the AC interface. According to the nature, there are nonlinear distortion and linear distortion.Linear distortion refers to the change in the amplitude and phase relationship between signal frequency components, and only the amplitude and phase distortion of the waveform appear. The characteristic of it is that no new frequency components are generated.Figure 1. Linear DistortionNon-linear distortion means that the signal waveform has been distorted and new frequency components have been generated.  Ⅱ Types of Audio Power Amp DistortionThe main points of distortion produced by audio power amplifiers are as follows:2.1 Harmonic Distortion (THD)🔸What is THD?This distortion is caused by non-linear components in the circuit. After the signal passes through these components, new frequency components (harmonics) are generated, which affect the original signal. The characteristic of this distortion is the input signal waveform inconsistent with the shape of the output signal. That is, the waveform is distorted. The following is a specific analysis.Harmonic distortion refers to the more harmonic components of the output signal than the input signal. It is caused by a system that is not completely linear. The sum of all additional harmonic levels is called total harmonic distortion, which is related to frequency. Generally speaking, at a frequency of 1000Hz, the distortion is the smallest. So many products confirm the distortion at this frequency as a indicator.Harmonic distortion is actually the distortion of the sound when the speaker reproduces the sound due to the resonance phenomenon that occurs during the working process of the speaker. Although only the fundamental frequency signal in the speaker is the original sound signal, due to the inevitable resonance phenomenon (the second, third and even multiple harmonics are generated on the basis of the original sound wave), there is no longer only the fundamental frequency signal in the sound signal, but also includes harmonics and their frequency multiplier components. These frequency multiplied signals will cause distortion when the speaker is playing. For ordinary speakers, a certain harmonic signal component is allowed, but it must be a prerequisite that it does not have a large impact on the sound fundamental frequency signal output.The total harmonic distortion usually expressed as a percentage. Generally speaking, the smaller the value, the better. Generally speaking, the THD value of high-quality equipment is very low (less than 0.002%), but there are exceptions. Many electronic tube devices have very high THD, but transistor devices must have low THD because their excess harmonics can make the sound uncomfortable.🔸How to Calculate THD?In the above formula, G represents the effective value of the harmonic component. It will be replaced by I when expressing current and U when expressing voltage as required. The value of H is given in each standard related to the limit. According to the above definition, THD does not include interharmonics, and there is a fixed upper limit of harmonics.In the above formula, Q is the total effective value, and Q1 is the fundamental effective value, which can represent the voltage or the current. According to the above definition, THD includes interharmonics and DC components.🔸How to Reduce THD?The main ways to reduce harmonic distortion are: 1) Apply an appropriate amount of negative feedback. 2) Choose amplifiers with high characteristic frequency, low noise figure and good linearity. 3) Increase the power reserve of the power supply and improve the filtering performance of it. 2.2 Intermodulation Distortion (IMD)🔸What is IMD?This distortion is usually produced by active devices in the circuit (such as transistors and tubes). Two or more signals of different frequencies pass through an amplifier or speaker to produce beats and form new frequency components. The magnitude of the distortion is related to the output power. Since these newly generated frequency components have no similarity with the original signal, the less intermodulation distortion is also easy to be noticed by the human ear.🔸How to Calculate IMD?The excitation signal used in the measurement technique of IMD is more than a single simple sinusoidal signal. In the fields of professional audio, broadcasting and consumer audio, two sine waves are used as excitation signals to measure it. When any two sine signals with frequencies of F1 and F2 are applied to the nonlinear device, the original two sine waves will be generated plus countless IMD terms, that is, countless combined frequency components, as shown in the following formula: mF1±nF2Where m and n are any positive integers. The order of any particular IMD value is the sum of m and n. The order of some terms are listed below:F1-F2 2nd order (even order)F1+F2 2nd order (even order)2F1-F2 3rd order (odd order)F1-2F2 3rd order (odd order)2F1+F2 3rd order (odd order)3F1-F2 4th order (even order)3F1+2F2 5th order (odd order)…….The above "odd" and "even" refer to whether m+n is odd or even.The measurement method of IMD is actually the measurement of harmonic voltage components, and its formula is:Where, F1 is high frequency, F2 is low frequency.🔸How to Reduce IMD?Methods to reduce intermodulation distortion: 1) Use electronic frequency division to limit the working bandwidth of the amplifier circuit or loudspeaker, thereby reducing the generation of beats. 2) Choose a tube or circuit structure with good linearity. 2.3 Transient Distortion Transient distortion is an important indicator of modern acoustics. It reflects the ability of the power amplifier circuit to keep track of transient signals, so it is also called transient response. This kind of distortion makes music lack level or transparency, and there are two forms of expression:🔸A. Transient Intermodulation Distortion (TIM)When inputting a pulsed transient signal, the output terminal cannot get the proper output voltage immediately due to the capacitance in the circuit, and the negative feedback circuit cannot get a timely response. The amplifier is in an open loop state at this moment, making the output instantaneous. Clipping occurs due to overload. This clipping distortion is called transient intermodulation distortion, and it is more serious on transistor machines.Transient intermodulation distortion is a dynamic indicator of the power amplifier, which is mainly caused by the deep negative feedback inside the power amplifier. It will affect the sound quality of the stone machine and cause "transistor noise" and "metal noise".The main methods to reduce this distortion are as follows: 1) The TIM can be eliminated by controlling the gain within the delay time of the negative feedback amplifier. 2) Multistage negative feedback can be used, so it is not easy to cause TIM due to fast feedback time and short path.3) Take well anti-interference measures.🔸B. Distortion Caused by Too Low Conversion RateAs mentioned above, high-level input pulses cause the amplifier to clip and then cause transient intermodulation distortion. Will low-level input pulses cause distortion? It depends on the response time of the amplifier. Because the response time of the amplifier is too long, the change of the output signal of the amplifier cannot keep up with the rapid change of the input signal. The transient distortion is caused by the low conversion rate. It reflects the response speed of the amplifier to the signal. This low-distortion amplifier has very good sound quality resolution, layering and positioning. 2.4 AC Interface DistortionThe distortion of the AC interface is caused by the back EMF of the speaker (the electric potential generated by cutting the magnetic lines of force when the speaker sounds vibration) feedback to the circuit.The improving methods are:1) Reduce the output impedance of the circuit.2) Choose a suitable speaker to make the damping coefficient more reasonable.3) Reduce the internal resistance of the power supply. Ⅲ ConclusionFor different types of audio power amplifiers, due to the differences the circuit itself, their sound is different. Transistor power amplifiers are affected by odd harmonic distortion and transient intermodulation distortion, and the sound will be cold, straightforward, burr or metallic. The sound of the tube amplifier is warm, thick, and stretched. So far, the electronic tube is still the active amplifier device with the best linearity and the smallest native distortion, and the transistor cannot be compared. But in fact, the total harmonic distortion (THD) of the tube power amplifier is several orders of magnitude larger than that of the transistor power amplifier. This is because it is difficult to add sufficient negative feedback to improve the linearity of the tube power amplifier. Most of these non-linear distortions are even harmonics that are pleasing to the ears, but they make people feel pleasant to the ears. The transistor power amplifier uses a large loop deep negative feedback to significantly improve the linearity. Due to the stability requirements, a compensation capacitor is introduced as the main pole. However, it may cause a problem of poor transient response. With the advancement of technology, the sound quality of integrated chip audio power amplifiers is getting closer and closer, even surpassing the above two types of power amplifiers, and it also has obvious advantages in terms of volume, cost, and scope of application. Ⅳ FAQ1. What is power amp distortion?The short answer is that power amp distortion derives from overloading/distorting an amplifier's power section. After the preamp portion of an amplifier is 'done' with the signal, it is then passed on to the phase inverter and out to the amp's power tubes. 2. Why is my amp distortion?You can create distortion by merely increasing the volume of your guitar and setting the input gain high enough on your amplifier. This combination of volume and preamp gain will create distortion as explained above, the gain exceeding the voltage capacity, causing the sound waves to clip. 3. Is amp distortion better than pedal distortion?Distortion pedals are considered more versatile with more parameters to shape your ideal sound. Their downfall is that some cheap pedals can sound unnatural. In contrast, the majority valve amp distortion provides a more, smoother, and overall, more well-rounded distortion. 4. How do I adjust the distortion on my amp?Turn knobs marked "gain" or "overdrive" all the way up. Turn other volume knobs down to get the loudness you want. Once you've proved you can get heavy distortion, dial things back to find the tone you want. Some amps won't distort at low volumes. 5. Do amps have built in distortion?The answer to the question do all guitar amps have distortion is no; not all guitar amps have distortion. In fact, there are different categories you could place guitar amps in depending on how they generate their distortion. 6. Does preamp reduce distortion?Preamp distortion generally offers higher gain than power amp distortion and is more compressed and smoother, with higher sustain at lower volume levels. ... In general, vintage-style amps sound best when driven into power amp distortion — depending on the amp, its preamp may not even be able to distort. 7. Do tube amps need distortion pedals?Most tube amps won't need a distortion pedal, digital or otherwise. When an amp has both a dirty (gain) and a clean channel, this allows you to dial your distorted tones along with whatever clean sound you might want to use. 8. Can you use a distortion pedal without an amp?Most modern multi-effects pedals have a jack where you can plug in any speakers or headphones. This means you can play an electric guitar without an amp by using a multi-effects pedal. Simply plug your guitar into a suitable multi-effects pedal and plug headphones or speakers into the pedal. 9. What amp is good for distortion?Top 5 Amps for Creating Clean and Distortion Sounds1) Orange Micro Terror2) Blackstar HT1R3) Peavey Vypyr VIP 14) Fender Champion 205) Marshall MG50CFX 10. Why is my audio distorted?The most common reason for distortion is an input overload like the microphone overload mentioned above. Mic'ing an instrument, or even a vocal, is more than sticking a microphone right up to the sound source. ... A distorted sound can be resolved by placing a greater distance between the sound source and the microphone.