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IntroductionThe operational amplifier is an integrated circuit that has two input pins and one output pin. It is used to amplify and output the voltage difference between the two input pins. Based on its characteristics, operational amplifier has different functions in different circuits. Here introduces common and fundamental op amp circuits examples with descriptions.A Basic Introduction to Op Amp CircuitsCatalogIntroductionOp Amp Diagram and Circuit Analysis1.1 What is the Inverting & Non-inverting Amplifier?1.2 Differential Amplifier1.3 Summing Amplifier1.4 Practical Differentiator1.5 Op-amp Integrator1.6 Converter, Detector, Bias Current Compensation, Voltage Comparator1.7 Offset Voltage Adjustment1.8 Sine Wave Generator1.9 Op-Amp Voltage Reference1.10 Instrumentation Amplifier1.11 Precision Current Sink & Source1.12 Precision Diode & Clamp1.13 Notch Filter Amplifier1.14 Capacitance Multiplier2 Other Op-amp Circuit ApplicationsOp Amp Diagram and Circuit AnalysisHow do you build an op amp circuit? This part introduces the most basic operational amplifier circuits. Understand the role of op amp in different circuits, and do reference design for your own amplifier circuit through the description of the op amp equations. What’s more, you can handle the most common op amp applications through these circuits.1.1 What is the Inverting & Non-inverting Amplifier?Figure 1. Inverting AmplifierIn an inverting amplifier circuit, the operational amplifier inverting input receives feedback from the output of the amplifier. Assuming the op-amp is ideal and applying the concept of virtual short at the input terminals of op-amp, the voltage at the inverting terminal is equal to non-inverting terminal. Figure 2. Inverting Amplifier with High Input ImpedanceIn electronics, high impedance means that a point in a circuit (a node) allows a relatively small amount of current through. For an inverting amplifier, the input impedance is approximately equal to the input resistance. This is because the input resistor is connected to “virtual ground” in the inverting configuration.Another Example:Figure 3. Fast Inverting Amplifier with High Input Impedance Figure 4. Non-inverting AmplifierA non-inverting amplifier is an op-amp circuit configuration which produces an amplified output signal. This output signal of non-inverting op amp is in-phase with the input signal applied. In other words a non-inverting amplifier behaves like a voltage follower circuit.Another Example:Figure 5. Non-inverting AC AmplifierRecommended Readings: Inverting and Non-inverting Amplifier and Their Basics......(1)Op Amp High Input Impedance and Low Output Impedance......(2)1.2 Differential AmplifierFigure 6.The differential amplifier circuit is a very useful op-amp circuit and by adding more resistors in parallel with the input resistors. It usually has two outputs and two inputs, which is a special purpose amplifier designed to measure differential signals, otherwise known as a subtractor. 1.3 Summing AmplifierThe Summing Amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage.Example Explained:Figure 7. Fast Summing Amplifier with Low Input Current Figure 8. Inverting Summing AmplifierThe inverting summing amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage. When the summing point is connected to the inverting input of the op-amp the circuit will produce the negative sum of any number of input voltages. Figure 9. Non-inverting Summing AmplifierThe non-inverting summing amplifier is a similar configuration to the inverting summing amplifier. In other words, it is based around the configuration of a non-inverting operational amplifier circuit in that the input (either ac or dc) is applied to the non-inverting (+) terminal, while the required negative feedback and gain is achieved by feeding back some portion. 1.4 Practical DifferentiatorFigure 11.A practical differentiator amplifier is basically a high pass filter and are used in wave shaping circuits, frequency modulators etc. Because differentiators have frequency limitations while operating on sine wave inputs; the circuit attenuates all low frequency signal components and allows only high frequency components at the output. In other words, the circuit behaves like a high-pass filter. 1.5 Op-amp IntegratorAn op-amp integrator is an electronic integration circuit that performs the mathematical operation of Integration, that is we can cause the output to respond to changes in the input voltage over time as the op-amp integrator produces an output voltage which is proportional to the integral.Figure 12. Fast Integrator Figure 13. Fast Integrator with Low Input Current Figure 14. Low Drift IntergratorIn Low Drift Intergrator circuit, the output of an operational amplifier always contains signals that could not have been predicted, even with knowledge of the input and an accurately. 1.6 Converter, Detector, Bias Current Compensation, Voltage ComparatorFigure 15. Current to Volatge ConverterA current to voltage converter will produce a voltage proportional to the applied input current. This circuit is required if your measuring instrument is capable only of measuring voltages and you need to measure the current output. Figure 16. Precision AC to DC ConverterA simple full wave precision rectifier using a single supply operational amplifier in saturation mode, which is to insure precision half wave rectification and unidirectional current flow. Figure 17. Temperature Compensated Logarithmic ConverterA temperature compensated logarithmic amplifier for signal strength indicator or automatic gain control applications is presented.  Figure 18. Double-Ended Limit DetectorThe circuit in see a differential Input to single ended output amplifier will convert a differential (double ended) signal. Figure 19. Fast Zero Crossing DetectorA zero-crossing detector whose input is a sign wave has been converted into a train of positive pulses at interval T by adding a RC network and a clipping. It can be used to detect phase anomalies, or even as a 'loss of AC' detector, purposes of synchronization, fast and accurate frequency. Figure 20. Low Drift Peak DetectorOp-amp based peak detector circuit is the modification of basic peak detector circuit, used to remove the voltage drop across the diode. It stores the peak value of input voltages for infinite time duration until it comes to reset condition. Figure 21. Op Amp Integrator with Bias Current CompensationThe operational amplifier integrator is an electronic integration circuit, where the resistor producing a compensating current flow through the series capacitor to maintain the virtual ground. Figure 22. Voltage Comparator for Driving DTL or TTL Integrated CircuitHigh frequency performance at any gain as a comparator the output can be drived DTL or TTL integrated circuit. Figure 23. Threshed Detector for PhotodiodesUse operational amplifiers or op-amps to convert the photodiode current to a measurable voltage. 1.7 Offset Voltage AdjustmentThe input offset voltage is defined as the voltage that must be applied between the two input terminals of the op amp to obtain zero volts at the output. Ideally the output of the op amp should be at zero volts when the inputs are grounded. The presence of offset can be encapsulated by assuming that the real Op Amp input/output transfer characteristic is y = A (V + – V – + e ) where e is the error in the differential input to the ideal Op Amp.Figure 24. Offset Voltage Adjustment for Inverting Amplifiers Using Any Type of Feedback Element Figure 25. Offset Voltage Adjustment for Non-inverting Amplifiers Using Any Type of Feedback Element Figure 26. Offset Voltage Adjustment for Voltage Followers Figure 27. Offset Voltage Adjustment for Differential Amplifiers Figure 28. Offset Voltage Adjustment for Inverting Amplifiers Using 10kΩ Source Resistance or Less 1.8 Sine Wave GeneratorSine Wave Generator Using Op AmpThe Sine Wave Generator is a type of electronic equipment that generates an oscillating frequency in a sinusoidal pattern. One of the popular methods of generating a sine wave with an operational amplifier is to use the Wien bridge configuration.Figure 29. Low Frequency Sine Wave Generator with Quadrature Output Figure 30. High Frequency Sine Wave Generator with Quadrature Output 1.9 Op-Amp Voltage ReferenceA voltage reference, or a VREF, is a precision device designed to maintain an accurate, low noise, constant output voltage. Ideally, the output should remain constant even as parameters, such as ambient temperature, supply voltage, or the load current change.Figure 31. Positive Voltage ReferenceIn a positive voltage reference a non-inverting op-amp buffer is often included to scale the output voltage and supply any current needed. Figure 32. Negative Voltage ReferenceA common way to generate a negative voltage has been to use an operational amplifier (op amp) to invert the output of a positive precision voltage reference. This approach typically requires a positive reference, the op amp, and two supply rails to generate the negative output. 1.10 Instrumentation AmplifierInstrumentation amplifier is a kind of differential amplifier with additional input buffer stages. It is a differential op-amp circuit providing high input impedance with ease of gain adjustment. Basically, a typical Instrumentation Amplifier configuration consists of three Op-amps and several resistors.Figure 33. Differential-input Instrumentation Amplifier Figure 34. Variable Gain, Differential-input Instrumentation Amplifier Figure 35. Instrumentation Amplifier with ±100V Common Mode Range Figure 36. Instrumentation Amplifier with ±10V Common Mode Range Figure 37. High Input Impedance Instrumentation Amplifier 1.11 Precision Current Sink & SourceOp Amp can source or sink current.Sourcing current means that current is flowing out of the op-amp into the load. Sinking current means that current is flowing in to the op-amp.Figure 38. Precision Current SinkFor a current sink circuit, opamp are designed to be used in both positive and negative voltages. The op-amp connection is changed, that is the negative input is connected to a shunt resistor. Figure 39. Precision Current SourcePrecision current sources have traditionally been built using op amps, resistors, and other discrete components—with limitations due to size, accuracy. Figure 40. Bilateral Current Source 1.12 Precision Diode & ClampFigure 41. Precision DiodeIn this circuit , the op-amp circuit is required to work as an ideal diode. That is, an ideal op-amp wants to make its two inputs equal in voltage through the negative feedback path. Figure 42. Precision ClampPrecision Op-Amp Clamp Circuit is the same circuit as the classic simple precision rectifier (set to pass the negative half-sine), but with the non-inverting input of the op-amp. 1.13 Notch Filter AmplifierNotch filter is a useful circuit to suppress middle- and high-frequency resonance to improve control precision. It work on only a narrow band of frequencies. To be useful, the notch filter must be tuned to the frequency of resonance or of noise generation.Figure 43. Adjustable Q Notch Filter Figure 44. Easily Tuned Notch Filter 1.14 Capacitance MultiplierCapacitance Multiplier uses an op-amp and a small capacitor to simulate a much larger capacitor instead of a transistor.Example Explained:Figure 45. Negative Capacitance Multiplier Figure 46. Variable Capacitance Multiplier Figure 47. Analog MultiplierIn electronics, an analog multiplier is a device which takes two analog signals and produces an output which is their product. Analog multipliers take two or more analog signals and produce an output which is their product or the sum of multiple products. 2 Other Op-amp Circuit DesignFigure 48. Free-Running MultivibratorThe Op-amp Multivibrator is an astable oscillator circuit that generates a rectangular output waveform using an RC timing network connected to the inverting end. An astable multivibrator uses an op-amp. It generates square waves of its own i.e. without any external excitation. Figure 49. Op Amp Function GeneratorFunction generator system can be readily synthesized using operational amplifiers on an approach which uses full when the need for a special need. Figure 50. Pulse-width Modulator (PWM)Pulse-width Modulator is a way to control analog devices with a digital output. It uses digital signals to control power applications, as well as being fairly easy to convert back to analog with a minimum of signal. High-frequency op amps can be used for a high-frequency PWM, because op amps are used for the modulator. Bridge AmplifierThe bridge amplifier is to generate both an inverted and a noninverted output signal. When the amplifier is switched into bridge-mode operation, the signal at the output of the first stage of amplification of channel A is attenuated. In addition, bridging an amplifier refers to the process of combining two of four channels into one or two channels with half the ohms.Figure 51. Bridge Amplifier with Low Noise Compensation Figure 52. Wien Bridge Sine Wave OscillatorA Wien bridge oscillator is a simple circuit that can be set to continuous oscillation, which outputs a sine wave. It acts as a useful reference oscillator for analog circuits, and the output signal can then be manipulated with other analog circuits. It is an excellent circuit for generating a sine wave signal at audio frequencies. Figure 53. Low Power Supply for Intergrated Circuit TestingOp-amp IC Testing Circuit basically has voltage comparator inside, which has two inputs, one is inverting input and second is non-inverting input. In normal, putting a good op-amp into the circuit, and they will generate a low frequency in the square wave. Figure 54. Fast Half Wave RectifierPrecision half-wave rectifiers are commonly used with other op amp circuits such as a peak-detector or bandwidth limited non-inverting amplifier to produce a DC output voltage. For the positive half cycle of the sinusoidal input, the output of the op-amp will be negative. Figure 55. Absolute Value Amplifier with Polarity DetectorAbsolute Value Amplifier with Polarity Detector Circuit breaks an input voltage signal down into its components. It will handle direct input voltages as well as alternating voltages up to several kHz. Figure 56. Sample and Hold Circuit Using Op AmpIn electronics, a sample and hold (also known as sample and follow) circuit is an analog device that samples (captures, takes) the voltage of a continuously varying analog signal and holds (locks, freezes) its value at a constant level for a specified minimum period of time. It consists of switching devices, capacitor and an operational amplifier. Figure 57. Tuned CircuitA tuned circuit has a very high impedance at its resonant frequency (ideally = infinity). At other frequencies, its impedance is lower. Tuned circuits are used to select or tune in radio stations on a particular frequency and reject all the others. When an amplifier circuit has its load replaced by a tuned circuit, such an amplifier can be called as a tuned amplifier circuit. It is generally referred to as active filters.Another Example:Figure 58. Two-Stage Tuned Circuit Figure 59. Simulated InductorA simulated inductor is an active circuit for generating an equivalent inductive reactance, which is implemented with active and passive components. It is used in the design of filters, amplifiers, oscillators and tuned amplifiers. Figure 60. High Pass Active FilterA high-pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with low frequencies. Active High Pass Filter uses inverting operational amplifier with high voltage gain. Figure 61. Low Pass Active FilterA simple active low pass filter is formed by using an op-amp. The operational amplifier will take the high impedance signal as input and gives a low impedance signal as output. The circuit uses an op-amp for amplification and gain control. Figure 62. Nonlinear OP AMP with Temperature Compensated BreakpointsAs long as the gain of the operational amplifier is large enough, the amplification of the circuit is determined by the external feedback resistance network. Figure 63. Current MonitorA current monitor amplifier is a special purpose integrated circuit differential amplifier that is designed to sense the voltage developed across a current shunt and output a voltage proportional to the measured current. Figure 64. Power Booster AmplifierA power booster amplifier is typically a hybrid circuit with thick film resistors, ceramic capacitors. A novel power booster amplifier is based on a modified half-bridge topology using separated switches and a floating bridge capacitor. Figure 65. Long Interval TimerWith the help of high gain high impedance operational amplifier, we can build a long time delay with resistor-capacitor (RC) circuit. Figure 66. Amplifier for Piezoelectric TransducerThe charge sensitive amplifiers employed for piezo electric sensors cover quite wide range. Piezoelectric transducers used as sensors, typically, the high impedance of the sensor requires an amplifier. Figure 67. Temperature ProbeAn inverting op amp operates with a noise gain of two, which produces twice as much output offset voltage as does a unity-gain buffer. This is a fantastic solution to temperature monitoring. Figure 68. Photodiode AmplifierPhotodiode amplifier circuit pedance amplifier for amplifying the light- dependent current of a photodiode. The high gain of the op-amp keeps the photodiode current equal to the feedback current. Some are ideally suited for ultra low noise amplification of very small photodiode currents. Figure 69. High Input Impedance AC FollowerOperational amplifiers have a very high input impedance, which means that they don't suck in much current (ideally, none) at the inputs, typically above 1MΩ as it is equal to that of the operational amplifiers input resistance. Low output impedance and extremely high input impedance make it a simple and effective solution to problematic impedance. Figure 70. Root ExtractorThe proposed extractor is based on the use of two operational amplifiers (op amps) as only active elements. Figure 71. Basic Log AmplifierA logarithmic amplifier, or a log amplifier, is an electronic circuit that produces an output that is proportional to the logarithm of the applied input. The simple logarithmic amplifier uses a junction diode as a nonlinear element. In addition, the basic log amplifier can also be constructed by replacing diode by a transistor. The output is proportional to the logarithm of the input given by. Figure 72. Circuit for Operating the LM101 without a Negative Supply Figure 73. Circuit for Generating the Second Positive Voltage Figure 74. Multiple Aperture Window Discriminator Figure 75. Neutralizing Input Capacitance to Optimize Response Time Figure 76. Saturating Serve Preamplifier with Rate FeedbackFrequently Asked Questions about Op Amp Circuits1. What is an op amp circuit?An operational amplifier is an integrated circuit that can amplify weak electric signals. An operational amplifier has two input pins and one output pin. Its basic role is to amplify and output the voltage difference between the two input pins. 2. Why use an op amp in a circuit?To convert the current into voltage, a simple circuit with an operational amplifier, a feedback loop through a resistor on the non-inverting, and the diode connected between the two input pins allows you to get an output voltage proportional to current generated by the photodiode, which is evident by the light. 3. How do op amp circuits work?An operational amplifier, or op amp, generally comprises a differential-input stage with high input impedance, an intermediate-gain stage, and a push-pull output stage with a low output impedance. ... That is, the output gets fed back to the inverting input through some impedance. 4. What are the advantages of op amps circuit?An op-amp circuit buffers the sensor and allows gain or attenuation circuits to be developed. The output of the sensor is non-linear. An inverting op amp circuit gives you a more linear output than a non-inverting op-amp circuit does. 5. What are the ideal characteristics of op amp?The so-called ideal op amp is to idealize various technical indicators of op amps, and it must have the following characteristics.1) Infinite Input Resistance2) Zero Output Impedance3) Infinite Open-loop Gain4) Infinite Common-mode Rejection Ratio5) Infinite Bandwidth

IntroductionIn electronics, a comparator is an electronic circuit that compares two voltages (or currents) and outputs a digital signal indicating which is larger. Comparing two or more data to determine the number size and arrangement order between them. In addition, it is a circuit that compares an analog voltage signal with a reference voltage. The two inputs of the comparator are analog signals, and the output is a binary signal 0 or 1, and the output is ideally. When the difference of the input voltage changes and the positive and negative sign remains constant, the output remains unchanged. Comparators play an essential role in designing electrical and electronic projects.What is A Comparator?CatalogIntroductionⅠ Working PrincipleⅡ Main Parameters2.1 Hysteresis Voltage2.2 Bias Current2.3 Super Power Swing2.4 Drain-source Voltage2.5 Output Delay TimeⅢ Comparator Classification3.1 Voltage Comparator3.2 Window Comparator3.3 Hysteresis ComparatorⅣ Comparator ICsⅤ How Do You Select a Comparator?Ⅵ Comparator Applications6.1 Zero-crossing Comparator 6.2 Relaxation Oscillator (ROSC)6.3 A/D Converter6.4 Voltage ComparatorⅦ Op Amp ComparatorⅠ Working PrincipleGenerally, in electronics, the comparator is used to compare two voltages or currents which are given at the two inputs of the comparator. A comparator circuit compares two voltages and outputs either a 1 (the voltage at the plus side; VDD in the illustration) or a 0 (the voltage at the negative side) to indicate which is larger. The operational amplifier can be used as a comparator theoretically without negative feedback. However, the open-loop gain of the operational amplifier is very high, so it can only process signals with a very small input differential voltage. Moreover, in general, the delay time of the op amp is long, which cannot meet the actual requirements. The comparator can be adjusted to provide a very small time delay, but its frequency response characteristics will be limited. To avoid output oscillation, many comparators also have internal hysteresis circuits. The threshold of the comparator is fixed, some have only one threshold, and some have two thresholds.Comparator SymbolⅡ Main Parameters2.1 Hysteresis VoltageThe voltage between the two input terminals of the comparator will change the output state when it crosses zero. Because the input terminal is often superimposed with a small voltage fluctuation, the differential mode voltage generated by it will cause the comparator output to change frequently.  In order to avoid output oscillation, the new comparator usually has a hysteresis voltage of several mV. The existence of it requires two switching points of the comparator: one is used to detect the rising voltage, the other is used to detect the falling voltage. The difference of the voltage threshold (VTRIP) is equal to the voltage hysteresis (VHYST). The offset voltage of hysteresis comparator is the average of TRIP and VTRIP-. The input voltage switching point of the comparator without hysteresis is the input offset voltage, not the zero of the ideal comparator. In addition, the offset voltage generally varies with temperature and power supply voltage. And the power supply rejection ratio is usually employed to express the influence of power supply voltage changes on the offset voltage.2.2 Bias CurrentThe input impedance of an ideal comparator is infinite. Therefore, there is no effect on the input signal theoretically. However, the actual input impedance of the comparator cannot be infinite. There is a current at the input end that flows through the internal resistance of the signal source and flows into the comparator, thereby generating an additional voltage difference. The bias current (Ibias) is defined as the median of the input currents of the two comparators and is used to measure the effect of input impedance.2.3 Super Power SwingTo further optimize the operating voltage range of the comparator, Maxim uses the parallel structure of the NPN tube and the PNP tube as the input stage of the comparator. Thus the input voltage of the comparator can be expanded. In this case, the lower limit can be lower to the lowest level, and the upper limit is 250mV higher than the power supply voltage to reach the Beyond-the-Rail standard. The input of this comparator allows a larger common-mode voltage.2.4 Drain-source VoltageThe comparator has only two different output states (zero level or power supply voltage). Its output stage of the comparator with full power swing characteristics is an emitter follower, which makes its voltage difference smaller between input and output signals. The voltage difference depends on the emitter junction voltage under the saturation state of the internal transistor of the comparator, which is equal to the drain-source voltage of the MOSFFET.2.5 Output Delay TimeIt includes the transmission delay of the signal through the components and the rise time and fall time of the signal. For high-speed comparators, such as MAX961, the typical value of the delay time can reach 4.5ns and the rise time is 2.3ns. Pay attention to the influence of different factors on the delay time when designing, including the influence of temperature, capacitive load, input overdrive and so on.Although the comparator has different types. The design and construction of each should take care of ordinary uses without affecting its measuring accuracy. The instrument should be very sensitive and withstand a reasonable ill usage without permanent harm.Ⅲ Comparator ClassificationComparators are classified into various kinds, such as electronic, electrical, mechanical, optical, sigma, digital and pneumatic comparators. These are used in various applications. Here we are talking about electronic comparator.3.1 Voltage ComparatorA voltage comparator is a circuit that discriminates and compares input signals, and is a basic unit that forms a non-sine wave generating circuit. Voltage comparators are commonly used including single-limit comparators, hysteresis comparators, window comparators, and three-state voltage comparators. Voltage comparator can be used as an interface between analog circuits and digital circuits, as well as waveform generation and conversion circuits.3.2 Window ComparatorCombine two comparators to form a "window comparator", which is widely used. The window comparator can set the upper limit voltage and lower limit voltage of the input at the same time, within limited voltage range, or outside the range, which we need. When the potential level of the high-level signal is higher than a certain specified value VH, it is equivalent to the positive saturation output of the comparator circuit. When the potential level of the low-level signal is lower than a certain specified value VL, it is equivalent to the negative saturation output of the comparator circuit. The comparator has two thresholds, and the transmission characteristic curve is window-shaped, so it is called a window comparator.3.3 Hysteresis ComparatorIt is a comparator with hysteresis loop transmission characteristics, and can be understood as a single-limit comparator with positive feedback. When the input voltage vI gradually increases from zero and VI is less than VT, the comparator output is a positive saturation voltage, and VT is called the upper threshold (trigger) level. When the input voltage VI>VT, the comparator output is a negative saturation voltage, and VT is called the lower threshold (trigger) level.Ⅳ Comparator ICsCommon chips are LM324, LM358, uA741, TL081234, OP07, OP27, which can all be made into voltage comparators (without negative feedback). LM339 and LM393 are professional voltage comparators with fast switching speed and small delay time, which can be used in special voltage comparison occasions. Ⅴ How Do You Select a Comparator?The working principle of a comparator is simple and straightforward. It has a positive pin and a negative pin. When the voltage on the positive pin is high, the output drives a signal. When using open-collector output, the output pin of the comparator is the collector of a transistor or the drain of a FET. When using push-pull output, the comparator has a complementary NPN/PNP stage, like in an operational amplifier. The open-collector output is used when the load and the comparator use different power supplies. This kind of scheme can realize the solenoid of 12V, although the comparator may only work at 3.3V. Another function of the open-collector output is to minimize the quiescent current when the output is turned off. Among them, no base current flows in the N-type output transistor, and some base current always flows through one of the two output transistors.However, open-collector output also has some disadvantages. For example, they require external pull-up resistors. These resistors must complete the pull-up task during the high-impedance period, so that when the output is lower than turn-off, the comparator can switch faster, and the pull-up resistor makes the output high. Therefore, when you need a symmetrical waveform, it is not suitable to use an open collector output, such as a clock recovery circuit. If your circuit does not require level conversion, you should choose push-pull output, such as ALD2321APC, it can provide 24mA output drive capacity, quiescent current is 90μA.The high-speed comparator may also have a latched output, so that the output can be kept in a known state to meet the set-up and hold time requirements of the digital input behind it. Once the digital part has read the output of the comparator, the latch pin can be released and the output can track the input.High-speed comparators may also use ECL (emitter coupled logic) levels from -5V to 0V. PECL (positive emitter coupled logic) outputs have the same voltage swing, from 0V to 5V. There is also RSPECL (reduced amplitude PECL) output. The two output pins of some high-speed comparators use LVDS (low-voltage differential signaling) output, which converts 300mV around a 1.2V common-mode voltage in a complementary manner. You can send these outputs directly to the LVDS input pins of FPGA (field programmable gate array) and other digital circuits.In production, CMOS technology is generally used to build low-power devices, while bipolar devices are used to build high-speed devices. This represents a basic compromise: high-power high-speed, accurate devices, and low-power, low-speed devices. Another compromise is gain and high speed. The low-power comparator may take 70µs conversion time and consume less power. The response time of the high-speed comparator is 150ps. Some devices can overcome the trade-off between speed and power consumption. When converting at the highest rate, the power consumed by the comparator is much higher than its static power consumption. In the static state, the current is low. When the comparator is operated at a higher speed, it must be able to charge the capacitor. In dynamic mode, the current increases as the working speed increases. Another factor in power consumption is the load on the chip. For a switching current, the capacitance will also become a load, and the capacitive and resistive components in the load must be considered. Many devices are related to broken pins, which can reduce the power consumption to less than 1µA.As with all simulation, the declared propagation delay is meaningful only under strictly defined conditions, because the degree to which the input pin is driven directly affects the propagation delay. The greater the overdrive, the faster the device. Dispersion is the range of propagation delay values of a device under various overdrive levels. The relationship between overdrive and speed is one reason why some engineers are reluctant to consider comparator speed as a function of slew rate. It necessary to define the output level that is quantized as a valid transition, usually the maximum output level is 10% to 90%. The slew rate also represents a requirement for overdrive, that is, to keep the propagation delay as short as possible.Another parameter to consider when choosing a comparator is noise. However, manufacturers often omit noise specifications of the comparators and instead use random jitter to measure noise. In addition to the noise signal passing through the device gain, the input aperture error and the output rise and fall time can also affect jitter. A clock-driven device is nothing but a lower gain comparator optimized for noise. Designers can use larger input transistors in a CMOS device to reduce flicker noise, but this method increases the input capacitance.The next consideration should be the rated voltage of the comparator. One factor related to the power supply interval is the allowable common-mode voltage at the input pins of the comparator. Some devices allow you to pull the output to a voltage range higher or lower than the power supply. For other devices, when you pull the input pin below the negative power rail, the output will be inverted. Comparator with rail-to-rail input stage expands the range of input common-mode mode. These devices have a dual-input stage, using N-type transistors or FETs in parallel with the P-type input stage. The input voltage of the P-type input stage operates at near the ground or the negative voltage rail, and the N-type input stage works when the input swings to the positive voltage rail. IC designers generally make the device switch between level 1 or 2V below the positive voltage rail. When sweeping over the rail-to-rail devices, some structures can minimize the offset voltage.Another important specification of the comparator is the input offset current, that is, the amount of current flowing into or out of the input pin when the device is working. CMOS products have a low offset current, which represents a mismatch in the leakage of the input pin ESD (electrostatic discharge) structure. For every 10°C increase in temperature, the input offset current doubles. The offset current of high-speed comparators can be obvious, but it is not a problem because low-impedance circuits are generally used to drive these high-speed comparators. The input offset current of a bipolar device depends on the relationship between the two inputs. In a comparator, a 60mV difference in the base voltage of a differential input pair will get a 10 times higher difference between the pair's collector current and the input offset current. Therefore, one pin can pull or sink twice the rated input offset current, while the other pins have almost no input offset current, depending on which pin has a higher voltage.Ⅵ Comparator Applications6.1 Zero-crossing Comparator The zero-crossing comparator is used to detect whether an input value is zero. The principle is using a comparator to compare two input voltages. One of the two input voltages is the reference voltage Vr and the other is the voltage to be measured Vu. Generally, Vr is connected from the non-inverting input terminal, and Vu is connected from the inverting input terminal. According to the result of comparing the input voltage, the forward or reverse saturation voltage is output. When the reference voltage is known, the measured result of the voltage can be obtained. When the reference voltage is zero, it is a zero-crossing comparator.The zero-crossing comparator has a small measurement error. When the product of the voltage difference between the two input terminals and the open-loop magnification is less than the output threshold, the detector will give a zero value. For example, when the open-loop magnification is 106 and the output threshold is 6v, if the voltage difference between the two input stages is less than 6 microvolts, the detector outputs zero. This can also be considered the uncertainty of measurement.6.2 Relaxation Oscillator (ROSC)Comparators can construct relaxation oscillators by using positive feedback and negative feedback. Positive feedback is a Schmitt trigger, which forms a multivibrator. The RC circuit adds negative feedback to it, which causes the circuit to start to oscillate spontaneously, making the entire circuit from a latch to a relaxation oscillator.Level shifting uses open-drain comparators (such as LM393, TLV3011, and MAX9028) to construct a level shifter to change the signal voltage. Choosing an appropriate pull-up voltage can flexibly get the converted voltage value. For example, use the MAX972 comparator to convert ±5V signals into 3V signals.6.3 A/D ConverterThe function of the comparator is to compare whether an input signal is higher than a given value. So it can convert the input analog signal into a binary digital signal. Almost all digital-to-analog converters (including delta-sigma modulation) contain comparators circuit to quantize the input analog signal.6.4 Voltage ComparatorThe voltage comparator can be regarded as an operational amplifier with an infinite amplification factor. The function of the voltage comparator: compare the magnitude of two voltages (using the high or low level of the output voltage to indicate the magnitude relationship between the two input voltages): When the voltage at the "+" input terminal is higher than the "-" input terminal, the voltage comparator output is high level; when the "+" input terminal voltage is lower than the "-" input terminal, the voltage comparator output is low level.It can be used as an interface between analog circuits and digital circuits, and can also be used as a waveform generation and conversion circuit. A simple voltage comparator can change the sine wave into a square wave or rectangular wave with the same frequency. The simple voltage comparator has a simple structure and high sensitivity, but its anti-interference ability is poor, so people have to improve it. The improved voltage comparators include: hysteresis comparator and window comparator. Operational amplifiers are used to determine "operational parameters" through feedback loops and input loops, such as magnification. The feedback amount can be part or all of the output current or voltage. The comparator does not need feedback and directly compares the quantity of the two input terminals. If the non-inverting input is greater than the inverted phase, the output is high, otherwise it outputs low. The input of the voltage comparator is a linear quantity, and the output is a switch (high and low level). In typical applications, a linear op amp can sometimes be used to form a voltage comparator without negative feedback. Ⅶ Op Amp ComparatorIn principle, operational amplifier can be used as comparator without negative feedback. However, because of its high open-loop gain, it can only process signals with very small input differential voltage. Moreover, in this case, the response time of the operational amplifier is much slower than that of the comparator, and it also lacks some special functions, such as hysteresis, internal reference and so on. Comparator usually can not be used as an operational amplifier. Comparator can provide minimal time delay after adjustment, but its frequency response characteristics are limited to some extent. Operational amplifier makes use of the advantage of frequency response correction to become a flexible and versatile device. In addition, many comparators also have internal hysteresis circuit, which can avoid output oscillation, but it can not be used as an op amp. Frequently Asked Questions about Comparator Electronics1. What is a comparator and its application?A comparator is an electronic component that compares two input voltages. Comparators are closely related to operational amplifiers, but a comparator is designed to operate with positive feedback and with its output saturated at one power rail or the other. 2. How does a comparator circuit work?The comparator circuit work by simply taking two analog input signals, comparing them and then produce the logical output high “1” or low “0“. ... When the analog input on non-inverting is less than the analog input on inverting input, then the comparator output will swing to the logical low. 3. What is the purpose of a comparator in op amp?Op-amp window comparators are a type of voltage comparator circuit which uses two op-amp comparators to produce a two-state output that indicates whether or not the input voltage is within a particular range or window of values by using two reference voltages. An upper reference voltage and a lower reference voltage. 4. How do you use comparator electronics?A comparator circuit compares two voltages and outputs either a 1 (the voltage at the plus side; VDD in the illustration) or a 0 (the voltage at the negative side) to indicate which is larger. Comparators are often used, for example, to check whether an input has reached some predetermined value. 5. What is comparator and its types?Comparators are classified into various kinds, such as electronic, electrical, mechanical, optical, sigma, digital and pneumatic comparators, these are used in various applications. Comparators play an essential role in designing electrical and electronic projects.

IntroductionA transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits. Its transmission current is AC. Transformer is commonly used to increase or decrease the supply. As one of the types, high-frequency transformers use frequencies from 20 KHz to over 1MHz. This paper tells the design process of high-frequency transformers (HFTs), that is, how to calculate high frequency transformer?How to Make High Frequency Transformer?CatalogIntroductionⅠ Transformer Core1.1 Magnetic Core Material1.2 Core Structure1.3 Core Parameters1.4 Coil Parameters1.5 Coil Turns1.6 Assembly Structure1.7 Temperature Rise CheckⅡ Types of High Frequency Transformer2.1 Transformer Classifications2.2 Design RulesⅢ Transformer Core Selection CaresⅣ Main Transformer ParametersⅤ How to Calculate High Frequency Transformer?5.1 Design Principles and Methods of Transformers5.2 AP Method Analysis5.3 Parameters of Power Supply5.4 Transformer Turns CalculationⅠ Transformer CoreIn real transformers, the two coils are wound onto the same iron core. The transformer core provides a magnetic path to channel flux. The use of highly permeable material (which describes the material's ability to carry flux), as well as better core construction techniques, helps provide a desirable, low reluctance flux path and confine lines of flux to the core. The following introduces some important aspect of the transformer core.1.1 Magnetic Core MaterialWhich material is best for high frequency transformer core? Soft ferrite is widely used in switching power supply due to its own characteristics. Its advantages are high resistivity, low AC eddy current loss, low price, and easy processing into various shapes. It also has disadvantages, including low working magnetic flux density, low permeability, large magnetostriction, and relatively sensitive to temperature changes. Choosing suitable materials can fully meet the design requirements of high-frequency transformers, and they have ideal performance and price advantage.1.2 Core StructureTransformer core as a main part, the factors to be considered when selecting the magnetic core structure are: reducing magnetic leakage and leakage inductance, increasing the heat dissipation spacing of the coil, which is beneficial to shielding, easy coil winding, and convenient assembly and wiring. Magnetic leakage and leakage inductance are directly related to the core structure. If the magnetic core does not require an air gap, a closed ring-shaped or square-shaped magnetic core is better.1.3 Core ParametersIn the design of the magnetic core parameters, special attention should be paid to the magnetic flux density on working not only limited by the magnetization curve, but also by the loss, and the working mode of power transmission. When the magnetic flux changes in one direction: ΔB=Bs-Br, which is not merely limited by the saturation magnetic flux density, but also mainly by the loss, (the loss causes a temperature rise to affect the magnetic flux density). Working magnetic flux density Bm=0.6～0.7ΔB.Opening the air gap can reduce Br to increase the magnetic flux density change value ΔB. After then, the excitation current increases, but the magnetic core volume can be reduced. For magnetic flux work in two-way: ΔB=2Bm. In this case, it is also necessary to pay attention to the fact that the volt-second area of the positive and negative changes of the excitation is not equal due to various reasons, and the DC bias problem occurs. Therefore, a small air gap can be added to the magnetic core, or a DC blocking capacitor can be added in the circuit design.1.4 Coil ParametersCoil parameters include the number of turns, wire section (diameter), wire form, winding arrangement and insulation arrangement.The wire diameter is determined by the current density of the winding. Usually J is 2.5～4A/mm2. The choice of wire diameter should consider the skin effect. If necessary, make adjustments after checking the temperature rise of the transformer.1.5 Coil TurnsGenerally used winding arrangement: The primary winding is close to the magnetic core, and the secondary winding feedback winding is gradually arranged outward. Two winding arrangements are recommended as following:1) If the voltage of the primary winding is high, and the secondary winding voltage is low, the secondary winding can be used close to the magnetic core, and next is the feedback winding, and the primary winding is in the outermost, which is beneficial to the primary winding to the magnetic core. Insulation arrangement.2) To increase the coupling between the primary and secondary windings, half of the primary windings can be close to the core, then the feedback winding and secondary windings, and another half primary windings in the outermost layer, which will reduce leakage inductance helpfully.1.6 Assembly StructureThe assembly structure of a high-frequency power transformer is divided into two types: horizontal and vertical. If using plane magnetic cores, chip magnetic cores and thin film magnetic cores, they all adopt a horizontal assembly structure.1.7 Temperature Rise CheckThe temperature rise check can be carried out by calculation and sample testing. The experimental temperature rise is lower than the allowable temperature rise by more than 15 degrees, increasing the current density and reducing the wire section appropriately. If it exceeds the allowable temperature rise, appropriately reduce the current density and increase the wire section. For example, increase the heat dissipation area of the magnetic core and wire diameter.Transformer SymbolⅡ Types of High Frequency Transformer2.1 Transformer ClassificationsPower transformers are divided into three categories according to the topology:(1) Flyback transformer(2) Forward transformer(3) Push-pull transformer (in full-bridge/half-bridge)The suitable topological structure of the magnetic core structure is shown in the table on the following:Core StructureTransformer Circuit TypeFlyback TypeForward TypePush-pull TypeE cores++0Planar E Cores-+0EFD Cores-++ETD Cores0++ER Cores0++U Cores+00RM Cores0+0EP Cores-+0P Cores-+0Ring Cores-++Remarks: "+"=Appropriate   "0"=Normal   "-"=None2.2 Design Rules1) If the DC filter inductor, and the inductor core only works in one quadrant, the inductors belonging to this type include Boost inductors, Buck inductors, Buck/boost inductors, forward and push-pull transformer filtering inductors, and single-ended transformers.2) The magnetic core of the forward transformer only works in one quadrant, so the transformer needs to be magnetically reset.3) The magnetic core of the push-pull transformer is bidirectional alternating magnetization. Converters belonging to this category include push-pull converters, half-bridge and full-bridge converters, and AC filter inductors. Ⅲ Transformer Core Selection Cares1) Soft ferrite is widely used in switching power supply due to its low price, good adaptability and high frequency performance.2) Soft ferrites are common in two series: manganese-zinc ferrite and nickel-zinc ferrite. The components of manganese-zinc ferrite are Fe2O3, MnCO3, and ZnO. It is mainly used in various filters below 1MHz, inductors, transformers, etc., with a wide range of applications. The components of nickel-zinc ferrite are Fe2O3, NiO, ZnO, etc., which are mainly used for various induction windings above 1MHz, anti-interference magnetic beads, and sharing antenna matching devices.3) Manganese-zinc ferrite cores are the most widely used in switching power supplies. Depending on their use, the choice of materials is also different. The cores used in the power input filter part are mostly high-permeability, and their material grades are mostly R4K～R10K, that is, ferrite cores with a relative permeability of 4000～10000. For main transformers and output filters, most of them have high saturation magnetic flux density, and their Bs is about 0.5T (ie 5000GS). Ⅳ Main Transformer Parametersa.Transformer TopologyWith a higher saturation magnetic flux density Bs and a lower residual magnetic flux density Br,  Bs has a certain impact on the transformer and winding results. Theoretically, if Bs is high, the number of winding turns will decrease, and the copper loss will also decrease. In practical applications, there are many circuit forms of switching power supply high-frequency converters. For transformers, their working forms can be divided into two categories:BipolarThe circuit is half-bridge, full-bridge, push-pull, etc. The positive and negative half-cycle excitation currents in the transformer primary winding are identical in magnitude and opposite in direction. Therefore, the magnetic flux changes in the transformer core also move symmetrically up and down. Maximum change range of B is △B=2Bm, and the DC component in the core basically cancels out.UnipolarThe circuit is single-ended forward, single-ended flyback, etc. The primary winding of the transformer adds a unidirectional square wave pulse voltage in one cycle (single-ended flyback is the case). The transformer core is unidirectionally excited, and the magnetic flux density varies from the maximum value Bm to the residual magnetic flux density Br. At this time, △B=Bm－Br. If Br is reduced and the saturation magnetic flux density Bs is increased, △B can be increased. It can reduce the number of turns and the copper loss. b. Low Power Loss at High FrequenciesThe power loss of ferrite not only affects the output efficiency of the power supply, but also causes the core heating, waveform distortion and other undesirable consequences. The heating problem of the transformer is extremely common in practical applications. It is mainly caused by the copper loss and core loss. If Bm is selected too low when designing the transformer, and more winding turns will cause the winding to heat up, and at the same time transfer heat to the magnetic core. Conversely, if the core is the main heating body, it will also cause the winding to heat up.When selecting ferrite materials, the power loss is required to have a negative temperature coefficient relationship. If the core loss is the main body of heat, the temperature of the transformer will rise, which will cause the core loss to increase further, eventually burn out the power tube, transformer and other components. Therefore, when developing power ferrites at home and abroad, it is necessary to solve the problem of the negative temperature coefficient of the magnetic material itself. This is also a significant feature of the magnetic material for power supply. c. PermeabilityHow much is the appropriate permeability? This should be determined according to the switching frequency of the actual circuit. Generally, materials with a relative permeability of 2000 have an applicable frequency below 300kHz, and sometimes it can be higher, less than 500kHz. For materials higher than this value, a lower magnetic permeability should be selected, generally around 1300. d. Higher Curie TemperatureThe Curie temperature is the temperature at which the magnetic material loses its magnetic properties, general above 200℃. However, the actual working temperature of the transformer should not be higher than 80℃. This is because when the temperature is above 100℃, its saturation magnetic flux density Bs has dropped to 70% of that at room temperature. Therefore, an excessively high operating temperature will cause the saturation flux density of the magnetic core to drop more severely. Furthermore, when it is higher than 100°C, its power consumption has a positive temperature coefficient, which will lead to a vicious circle. For the R2KB2 material, the temperature corresponding to its allowable power consumption has reached 110°C, and the Curie temperature is as high as 240°C, which meets the requirements for high-temperature use. Ⅴ How to Calculate High Frequency Transformer?5.1 Design Principles and Methods of TransformersThere are two principle methods for designing transformers: area product AP method. AP is the product of the core cross-sectional area Ae and the coil effective window area Aw.PT-power of transformerAe- effective cross-sectional areaAw- core window areaKo-core window utilization factor, typical value is 0.4.Kf-form factor, square wave is 4, and sine wave is 4.44.Bw-the working magnetic intensity of the magnetic coreFs-switch operating frequencyKj-current density coefficient, take 395A/cm2X-core structure coefficient5.2 AP Method AnalysisAccording to the design method of power transformer, the general steps of designing transformer with area product AP method:1. Select the core material and calculate the apparent power of the transformer.2. Determine the core cross-sectional size AP, and then select the core size according to it.3. Calculate the inductance and number of turns of the primary and secondary sides.4. Calculate the length of the air gap.5. Find the wire diameter according to the current density and the effective value current of the primary and secondary sides.6. Determine whether the copper loss and iron loss meet the requirements (allowable loss and temperature rise).5.3 Parameters of Power SupplyInput voltage: 175-264VACOutput voltage: 21VOutput power: 3AThe frequency is set at 60KHz, and the duty cycle is initially set at 0.45. Using a flyback topology, choose the core material and determine the apparent power PT of the transformer.Consider the cost, choose PC40 material here:Check the PC40 data and get Bs=0.39T, Br=0.06TBm= ΔBmax*0.6=0.198T, round it to 0.2TIn order to prevent the magnetic core from being saturated momentarily, reserve a certain margin and take Bm= ΔBmax*0.6=0.198T, take 0.2T.Transformer apparent power PT, for the flyback transformer:Calculate AP:Where:J is the current density, usually taking 395A/cm2.Ku is the effective use coefficient of the copper window, which is determined according to the safety requirements and the number of output channels, generally 0.2 to 0.4. Take 0.4 here to adapt to the sudden load current. The power supply is designed in critical mode, and the critical current I0B=0.8×I0=2.4A5.4 Transformer Turns Calculation1) Minimum input voltage: Vimin=ViACmin*1.2=210V2) Turns Ration=[Vimin/(Vo+Vf)]*[Dmax/(1-Dmax)]n=[210V/(21V+1V)]*[0.45/(1-0.45)]=7.83) Secondary Side Peak Current^IsB=2*IoB/(1-Dmax)^IsB=2*2.4A/(1-0.45)=8.72A4) Secondary Side InductanceLs=(Vo+Vf)*(1-Dmax)*[1/(Fs*1000)]/^IsB*1000000Ls=(21V+1V)*(1-0.45)*[1/(60KHz*1000)]/^8.72A*1000000=23.58uH5) Primary Side InductanceLp=n*n*LsLp=7.8*7.8*23.58uH=1434uH6) Secondary Side Peak Current (continuous mode)^IsB=Io/(1-Dmax)+(^IsB/2)^IsB=3A/(1-0.45)+(8.72A/2)=9.81A7) Primary Side Peak Current (continuous mode)^Ipp=^Isp/n^Ipp=9.81A/7.8=1.257APrimary Winding and Secondary Winding Turns1) Primary Winding TurnsNp=Lp*^Ipp(^B*Ae)Np=1434uH*1.257A/(0.2*84.8)=106.28T，round it to 106T2) Secondary Winding TurnsNs=Np/nNs=106T/7.8=13.58T，round it to Ns=14T3) Feedback TurnsNv=(Vcc+Vf)/[(Vo+Vf)/Ns]Nv=(14.5V+1V)/[(21V+1V)/14T]=9.87T, round it to Nv=10TIn order to avoid saturation of the magnetic core, an appropriate air gap is added to the magnetic circuit, and the calculation is as follows:It may be necessary to correct the number of turns based on the edge effect of the air gap flux.There are two methods for the wire diameter of the primary, secondary and auxiliary windings:Bare wire areaPrimary Winding diameter: effective currentIprms=Po/^n/ViminIprms=63W/0.8/210V=0.375AWire diameter (J current density is 4A/mm2)Use two 0.18mm diameter wires and wind them together, or use AWG #28 single stranded wire.Secondary winding diameterUse 4 wires with a diameter of 0.25mm to be wound in parallel and calculate the current skin depth:The wire diameter of multiple strands must be less than or equal to dwH. For single wire winding, if the wire diameter exceeds the dwH, it is necessary to consider the use of multiple strands.The calculation of copper loss Pcu and iron loss Pfe (transformer total loss Ploss)a) Primary winding and secondary winding losses. Among them, MLT is the average turn length of the magnetic core. b) Calculate the allowable total loss Ploss and iron loss under the efficiency η.c) Find the actual loss under the operation according to the core loss curve.Iron loss per unit weight, it actually occurredThe actual iron loss should be lower than the allowable value.d) Calculate the loss per unit area Φ=Ploss/As. If the temperature rise caused by the Φ value is less than 25 degrees, the design is good.Bw Calculation:The working magnetic flux density Bw should be met the design index requirements, Bw<Bs-Br, to avoid saturation of the magnetic core. Frequently Asked Questions about High Frequency Transformer Design1. What is high frequency transformer?The primary difference is that, as their name implies, they operate at much higher frequencies — while most line voltage transformers operate at 50 or 60 Hz, high-frequency transformers use frequencies from 20 KHz to over 1MHz. ... For any given power rating, the higher the frequency, the smaller the transformer can be. 2. What are the design aspects of high frequency transformer?Design of HF transformers. High frequency transformers transfer electric power. The physical size is dependent on the power to be transfered as well as the operating frequency. The higher the frequency the smaller the physical size. 3. What is the use of high frequency transformer?These transformers are designed to handle up to 15,000 volts safely and accurately, converting high voltage and current levels between coils by magnetic induction. High Voltage, High Frequency Transformers are relied on for applications ranging from power supplies to laser equipment and particle accelerators. 4. What is difference between high frequency and low frequency?When we talk about sound, we talk in terms of high and low-frequency waves. ... This measurement of cycles per second is expressed in Hertz (Hz), with a higher Hz representing higher frequency sound. Low-frequency sounds are 500 Hz or lower while high-frequency waves are above 2000 Hz. 5. What is the frequency of transformer?What is Transformer Frequency. The three common frequencies available are 50Hz, 60Hz and 400Hz. European power is typically 50Hz while North American power is usually 60hz. The 400 Hz is reserved for high-powered applications such as aerospace and some special-purpose computer power supplies and hand-held machine tools.

IntroductionEarthing (also known as grounding) refers to the process of transferring the immediate discharge of the electrical energy directly to the earth by the help of the low resistance wire, for safety and functional purposes. Generally, the "ground" of electronic equipment has two meanings: one is to connect to the "earth". Taking the earth as the zero potential, connecting the metal shell of electronic equipment and the circuit reference point to the earth can protect the safety of equipment and personnel, such as protective earthing, lightning protection earthing, etc. In addition, the earthing in the weak current system does not necessarily mean the ground connected to the earth in the true sense. It has the effect of improving the stability of the system, shielding and protecting the electromagnetic compatibility of the system, and it can also be connected to the "earth" when necessary.What is Electrical Earthing?CatalogIntroductionⅠ Earthing Basic1.1 Electrical Earthing1.2 Earthing SymbolsⅡ What Are the Types of Earthing?Ⅲ Why Is Electrical Earthing Important?Ⅳ Earthing Q&A You Should KnowⅠ Earthing Basic1.1 Electrical EarthingAn earthing system (UK and IEC) or grounding system (US) connects specific parts of an electric power system with the ground. Earthing is a therapeutic technique that involves doing activities that “ground” or electrically connect you to the earth. In modern earthing concepts, for line engineers, the meaning of this term is usually a reference point of line voltage; for system designers, it is often a cabinet or rack; for electrical engineers, it is safe earthing or connecting to the earth. A more general definition is a low impedance path for current to return to its source. Note that the requirements are "low impedance" and "path".1.2 Earthing SymbolsPE, PGND, FG: Protective ground or chassisBGND or DC-RETURN: Power supply (battery) returnGND: Work groundDGND: Digital groundAGND: Analog groundLGND: Lightning protection groundⅡ What Are the Types of Earthing?There are many types of earthing, including single-point earthing, multi-point earthing and mixed types of earthing. Among them, single-point earthing is divided into series earthing and parallel earthing. Generally speaking, single-point earthing is used for simple circuits, such as earthing distinctions between different functional modules, and low-frequency (f<1MHz) electronic circuits. When designing high frequency (>10MHz) circuits, multi-point earthing or multilayer boards (complete ground plane) should be used. The following are four specific earthing methods.1. Earth FloatingIn electronic design, a commonly used method is floating technology. In this method, the signal ground of the circuit board is not connected to the external public ground, thereby ensuring good isolation of the circuit. The circuit is well isolated from the external ground system and is not easily affected by the interference on the external ground system. However, static electricity is easy to accumulate on the circuit and cause electrostatic interference, which may generate dangerous voltage.Small-scale low-speed (<1mhz) equipment can use earth floating, a single-point connection to the ground by the metal shell.2. Single-point earthing in SeriesThis kind of earthing method is relatively simple, and there is no need to pay so much attention to the circuit board design. So it will be used more. However, this kind of circuit will have common impedance coupling, causing each circuit module to affect each other.3. Single point earthing in ParallelThis method of earthing, although getting rid of the common impedance coupling problem of series single-point earthing, but in actual use, it will introduce too much earthing wire annoying, as to which one needs to be comprehensively evaluated in the actual process. If the circuit board area allows, use the parallel mode, and if the connection between the various circuit modules is kept simple, then use the series mode. In general, there are power modules, analog circuit modules, digital circuit modules and protection circuit modules in the downloaded board. In this case, I use a parallel single-point earthing method.4. Multi-point EarthingMulti-point earthing is used more in daily circuit design, especially in multi-module circuit design. This earthing method can effectively reduce high-frequency interference problems, but it is also prone to cause earthing loops. This point must be fully considered in the design to improve the circuit stability. The working ground of small high-speed (>10MHz) equipment should be grounded at multiple points with its metal casing. The distance between earthing points should be less than 1/20 of the wavelength of the highest operating frequency, and the metal casing should be connected to the ground at a single point.In short, in the design of electronic circuits, the most important point is to reduce the loop area of the circuit, to improve the stability of electronic design and the EMC design of electronic systems. In the actual design, have comprehensive evaluation of the above various earthing technologies to achieve the purpose of improving system stability.Ⅲ Why Is Electrical Earthing Important?As for earthing function, the introduction of earthing technology was originally a protective measure to prevent electrical or electronic equipment from being struck by lightning. The purpose was to introduce the lightning current generated to the ground through the lightning rod, thereby protecting the building. At the same time, earthing is also an effective means to protect personal safety. When the phase line touches the equipment shell caused by some reason (such as poor insulation of wires, aging of wiring, etc.), the equipment shell will have dangerous voltages. The generated fault current will flow through the neutral line to the ground, thereby playing a protective role. With the development of electronic communication and other digital fields, it is no longer sufficient to consider only lightning protection and safety in the earthing system. For example, in a communication system, the interconnection of signals between a large number of devices requires each device to have a reference ground as the signal reference ground. And with the complexity of electronic equipment, the signal frequency is getting higher and higher. Therefore, in the earthing design, special attention must be paid to electromagnetic compatibility issues such as mutual interference between signals. Otherwise, improper earthing will seriously affect the reliability of system operation. Also, the concept of "earthing" has also been introduced in the high-speed signals return technology. Ⅳ Earthing Q&A You Should KnowThe following questions relay on electrical earthing science and grounding physics to explain how electrical charges from the earth can have huge effects on our life. And how do you discharge the electrical energy directly to the earth by earthing technology. Also these Q&A give you considerable attention for the earthing system design and installation.1. What is the difference between earth earthing and electrical earthing?The earth is an object with very low resistance and very large capacitance. It has the ability to absorb infinite charge, and meanwhile can maintain the potential unchanged. Therefore, it is used as the reference potential of a system electrically, that is electrical earthing. In addition, in electronic equipment, when transmitting current and signal conversion at various levels of circuits, a reference potential is required to prevent interference from external signals. This potential is called logical ground or floating ground.2. What is the difference between the ground potential and the logical ground potential?Since the earth can absorb infinite electric charge, the potential of the earth looks macroscopically zero. Due to the influence of the natural electric field and the artificial electric field in the earth, the potential of each point of the earth is different. In engineering, 20m away from the artificial electric field is regarded as zero potential (earthing potential). The electrical ground potential is related to the current injected into the ground by the electrical system. When a large current flows into the electrical ground, the electrical ground potential may reach a very high voltage, especially when the lightning current flows into the electrical ground. The instantaneous potential of the electrical ground can reach 100,000 volts. Therefore, a separate lightning protection earthing point cannot be located in a place where have pedestrians.3. What is the shell?Due to the damage of the insulation layer of the wire, the phase wire is in contact with the outer shell of the electrical equipment, which is called a bumping shell. If the insulation of the phase wires and the enclosure of the electrical equipment does not meet the specified requirements, the equipment cannot be put into use. The reason for the insulation drop may be moisture or damage to the insulation layer, which can be analyzed according to the environment in which the circuit equipment is used.4. What is the step voltage?When an electrical device has a short-circuit fault to the ground, the fault current flows from the fault ground to the ground electrode and returns to the power source. Therefore, an electric field is generated around the ground of the fault point and the ground electrode, which is away from the ground of the fault point or the ground of the ground electrode. The closer, the higher the potential, and the farther, the lower the potential. When the distance between the two feet of a person is about 0.8 meters, standing in this electric field, because the two feet are at different potential points, there will be a potential difference. This potential difference is called the step voltage.5. What is contact voltage?When the insulation of electrical equipment is damaged and a short-circuit occurs to the shell, people who touch the electrical equipment will have the risk of electric shock. To define the degree of danger, the potential of the equipment 0.8 meters away from the horizontal direction of the electrical equipment when it fails is measured. The potential difference between the two is called the contact voltage.6. What is the earthing resistance difference between the earthing electrode and the equipment?The ratio of the earthing voltage to the earthing current is called the earthing resistance of the earthing electrode. When measuring the earthing electrode resistance in a project, an ac voltage is artificially applied to the earthing electrode, and then the current flowing into the earthing electrode is measured. The ratio of the two is the earthing resistance. The earthing resistance of the equipment is the sum of earthing wires resistances.7. What are the classifications of earthing functions?Generally divided into two categories: protective earthing and functional earthing1) Protective earthing can be divided into the following 4 types:Protective earthing: earthing the exposed conductor part of the equipment is called protective earthing. Its purpose is to prevent electrical equipment insulation damage or leakage, which may cause electric shock when people touch it.Lightning earthing: Lead lightning into the earth to prevent electric shock or other property damage.Anti-static earthing: Introduce static charges into the ground to prevent the accumulation of static electricity from causing harm to the human body and equipment.Anti-corrosion earthing: Bury a metal body underground as a sacrificial anode or cathode to protect the metal body connected to it, such as a metal oil pipeline.2) Functional earthing can be divided into the following 4 types:Working earthing: In order to ensure the operation of the power system, earthing is done at an appropriate place in the power system, which is called working earthing. In an AC system, this point is generally a neutral point.Logic earthing: To obtain a stable reference voltage, the appropriate metal parts in the electronic equipment are used as the reference zero potential, and the electronic parts that need to obtain the zero potential are connected to this metal part. This method is called logic earthing.Shield earthing: Ground the metal shell or the metal net to protect the electronic equipment in the shell or the net from external electrical interference, or prevent the electrical equipment in the shell or the net from causing interference to external electronic equipment.Signal earthing: A earthing method set to ensure that the signal has a stable reference potential.8. What is working ground?In order to ensure the safe operation of the electrical device, the earthing of any point (usually the neutral point of the power supply) of the device conductive part is called the working ground.9. What is the relationship between the safety voltage and the use environment?The safety voltage is to prevent personal electric shock. The degree of electric shock is related to the impedance of the human body, and the impedance of the human body has a great relationship with the contact condition. Under different conditions, it is different.The relationship between human body impedance and contact conditions is usually divided into three categories:1) High impedance: dry skin, dry environment, high impedance ground2) Low impedance: moist skin, humid environment, low impedance ground3) Zero impedance: for example, the human body is immersed in water10. What is the difference between short circuit and ground fault?The electrical connection between mutually insulated live conductors due to insulation damage is called a short circuit. For example, between phase wires of different phases, or between a phase wire and a neutral wire, exist an electrical connection, there may be a short circuit. The electrical connection error between the live conductor and the earth is called a ground fault. In addition, live conductors refer not only to the phase line, but also the neutral line. The ground refers to the metal shell of grounded electrical equipment, non-electrical metal pipes and the earth.11. What parts of the earthing device consist of?earthing device is a general term for earthing electrode and earthing wire.The earthing electrode is a conductor buried in the soil or concrete foundation for dissipating current. It can be divided into two types: natural earthing electrode and artificial earthing electrode.There are several types of natural earthing electrodes: the underground metal plumbing systems, the metal structure of the building and the reinforced concrete structure.The artificial earthing electrode should adopt horizontally laid round steel, flat steel, metal earthing plate, and vertically laid angle steel, steel pipe, round steel, etc.12. What are the measures to prevent direct electric shock?Insulate charged objectsUse shields or barriers to block the human body from charged objectsUse leakage switch as additional protection13. What are the measures to prevent indirect electric shock?Set up automatic power-off deviceEquipment with double insulationTake ungrounded local potential connectionElectrical isolation14. What are the types of earthing systems for high-voltage systems?1) Direct earthing, that is, the neutral point of the transformer or generator is connected to the earthing device directly or through a small resistance (such as a current transformer). This kind of earthing method has a large earthing current when a single-phase earthing short circuit occurs, so it is also called the large current earthing system.2) Ungrounded, the neutral point of the transformer in this system is not grounded or connected to earthing equipment such as arc suppression coils, large resistances, and the earthing device.15. Can the natural earthing electrode be used for the earthing of DC electrical devices?The earthing of AC electrical installations should make full use of the natural earthing electrode buried in the ground. For the earthing of DC electrical installations, it is not allowed to use the natural earthing electrode as the PE wire, earthing wire and earthing electrode of the current pattern. The earthing device is connected to the natural earthing. The distance between earthing devices and AC electrical devices shall not be less than 1m to avoid electrical corrosion.16. What is the function of total equipotential bonding?The function of total equipotential bonding (MEB) is to reduce the contact voltage of indirect contact electric shock in the building and different metal parts with different potential, which eliminate the dangerous fault voltage introduced from outside the building through electrical lines and various metal pipes.17. What is supplementary bonding?The two conductive parts are directly connected with wires to make the contact voltage of the fault drop below the contact voltage limit, which is called supplementary or additional equipotential bonding (earthing). When the earthing device fails, the indirect contact protection conditions for automatically cutting off the power supply cannot be met, supplementary bonding should be set. It should also be installed in places with special requirements such as bathrooms, hospitals, and swimming pools.18. What is local equipotential bonding?Local equipotential bonding (LEB) refers to the connection of multiple supplementary equipotential bonding through the bonding terminals in a local board, which is called local equipotential bonding.19. How to check the conductivity of equipotential bonding?1) Welding quality inspection2) Bolt connection quality inspection3) Measure resistance between branch and trunk20. What are the characteristics of arc short circuits?There are two forms of short circuit and ground fault: metallic and arc short. The current of metallic short circuit is very large, which can make the overcurrent protector (circuit breaker or fuse) act in time and the fault is not easy to go on. The short circuit point of arc short circuit has arc or electric spark and the impedance is large, therefore, the short circuit current is small. So overcurrent protection will not take effect. However, the temperature of the arc short-circuit point is very high, which can reach thousands of degrees Celsius locally. It is very easy to ignite the substances around the short-circuit point and cause a fire.Arcing short circuit not only occur in electrical and earthing faults, but poor connections between wires can also cause it. For example, cause flickering of incandescent lamps or interference for TV sets. At this time, you must check whether the connection point of the line is reliable. Frequently Asked Questions about Electrical Earthing System Basics1. What is elecrical earthing and types of earthing?Earthing is the first step towards electrical safety. ... Earthing is done to provide safety to user from electric shock. It is a set of conductors connected in series or in parallel in order to dissipate the potential difference immediately into the ground. The wire connected from equipment to earth called earthing wire. 2. What is difference between earthing and grounding?The key difference between earthing and grounding is that the term “Earthing” means that the circuit is physically connected to the ground which is Zero Volt Potential to the Ground (Earth). Whereas in “Grounding” the circuit is not physically connected to ground, but its potential is zero with respect to other points.Difference between Earthing and Grounding 3. Is grounding the same as earthing?The key difference between earthing and grounding is that the term “Earthing” means that the circuit is physically connected to the ground which is Zero Volt Potential to the Ground (Earth). Whereas in “Grounding” the circuit is not physically connected to ground, but its potential is zero with respect to other points. 4. What is the purpose of earthing?Earthing is used to protect you from an electric shock. It does this by providing a path (a protective conductor) for a fault current to flow to earth. It also causes the protective device (either a circuit-breaker or fuse) to switch off the electric current to the circuit that has the fault. 5. Which wire is used for earthing?copper wiresEarthing Lead or Earthing JointEventhough copper wires are generally used as earthing lead, copper strips are preferred for high installation as it can carry higher values of fault current due to its wider area.

Ⅰ IntroductionThe energy storage units of several devices we come across every day are batteries; they are available in various shapes, sizes, parameters, and shapes. They can usually be found in vehicles, emergency power sources, mobile devices, tablets, iPads, and many other portable electronic devices. But not all devices will use the same type of battery; each device has its own specifications and power supply requirements, and to choose the right battery for your application, you will need a battery selection guide. So, the considerations to consider when choosing a battery for your next electronic product design will be investigated in this post. If you are completely new to batteries, then it is recommended that you read this article on battery types and their applications before continuing further to understand the fundamentals of batteries selection.CatalogⅠ IntroductionⅡ Some Factors to ConsiderⅢ Rechargeable / Non-Rechargeable BatteriesⅣ Availability of SpaceⅤ System Operating VoltageⅥ Operating TemperatureⅦ Capacity-Power & EnergyⅧ ChemistryⅨ CostⅩ Shelf LifeⅪ How to Choose a BatteryⅫ FAQⅡ Some Factors to ConsiderYou must be aware of the important parameters involved in its activity when selecting a battery for your application. The truth of the battery is that, because no battery is ideal, there is no common form of battery for all applications. You should be able to manage the exhaustion of other parameters when you choose to use one parameter of the battery.  For example, if you want your battery to provide a lot of energy for your application, the internal resistance of the cell should be reduced, which can only be accomplished by increasing the surface area of the electrode. Inactive components such as current collectors and conductive aid are also improved by this because energy density is traded off to gain power. You must give up anything to get the other in a battery in order to get exactly what you want in your application. In the following picture, the important battery parameters are given.Now, to understand its significance and effect on battery efficiency during service, let's briefly look at each battery parameter.Ⅲ Rechargeable / Non-Rechargeable BatteriesIn deciding between a main and secondary battery, there might not be much uncertainty, you only have to decide whether you want the battery to be used once or several times. The primary (non-rechargeable) battery can be used for occasional applications such as toys, flashlights, smoke detectors, etc. They are also used in products such as pacemakers, wristwatches and hearing aids where charging is not feasible. The secondary (rechargeable) batteries can be used in applications where a standard power source such as cell phones, computers, cars, etc. is needed. Compared to primary batteries, secondary batteries often have a higher self-discharge rate because of their ability to recharge, which is an ignorant fact.Ⅳ Availability of SpaceThe batteries, including button cells, cylindrical cells, pouch cells and prismatic cells, are available in different shapes and sizes. In order to make your computer comfortably portable, the battery size really matters. AA, AAA and 9V batteries suitable for portable devices are the standard sizes available. In applications where there is less room but more power needed, lithium batteries (pouch type) are widely preferred. If the power demand is lower since they are very lightweight and the smallest of battery types, coin cells may also be considered.Ⅴ System Operating VoltageOne of the most significant characteristics of the battery, which is calculated based on the electrode & electrolyte used, is the battery voltage (Chemical Reaction). There is a common misconception that in any device, it is not the case that a fully discharged battery would have 0V. In fact, if the battery reads 0V, it's probably dead. A battery's output voltage should always be read from its nominal voltage level. Water is used as an electrolyte by the zinc-carbon battery and nickel-metal hydride battery and provides a nominal voltage of 1.2V to 2V, while the lithium-based batteries use organic electrolytes that can provide a nominal voltage of 3.2 to 4V. Most of the equipment's electronic parts run in the 3V voltage range. A single cell battery would be enough to power the equipment if you use a lithium-based battery. Note that the battery voltage will not be constant and will differ between the minimum value and the maximum value, depending on the battery power available. This is the minimum and maximum value shown below for each battery. Your nominal voltage would only be 3.2V to 4V if your circuit is running at 5V and you are charging it with a lithium battery. Boost converter circuits are used in these cases to convert the battery voltage required for the circuit to 5V. If your operating voltage is very high, like 24V or 12V, you can either use a 12V lead-acid battery or combine more than one lithium cell in series to increase the resulting output voltage if you need high power density.Ⅵ Operating TemperatureFor example, the battery operating with aqueous electrolytes can not be used in temperature conditions below 0 ° C as the aqueous electrolyte could be frozen below 0 ° C, in the same way,  the lithium-based batteries could work up to -40 ° C, but the efficiency could be reduced. The battery performance can be drastically modified by the temperature. The optimum charging rate for the lithium-ion batteries is between the temperature ranges of 20 ° C to 45 ° C. If you want to use a lower current/voltage outside this temperature range, this will result in a longer charge time. Lithium dendrite plating can be produced in the electrolyte if the temperature drops below 5 ° C or 10 ° C, which must be avoided by trickle charging.Ⅶ Capacity-Power & EnergyThe battery's strength determines the battery's runtime. Battery power/capacity is expressed in watt-hours (Wh). By multiplying the battery voltage (V) by the amount of current a battery can produce over a given amount of time, the watt-hour is determined. The battery voltage is almost set and the current that can be supplied by a battery is written on the battery, expressed in the Ampere-hour rating (Ah or mAh). Consider a 5V battery with a capacity of 2 amp-hours (Ah), so it has a power of 10Wh. The 2Ah battery will produce 2 Amps for 1 hour or 0.2A for 10 hours or 0.02A (20mA) for 100 hours. At a given discharge rate, temperature, and cut-off voltage, battery manufacturers often specify the power, where the capacity always depends on all three variables. A battery's capacity can tell us how much energy it can supply to an application. For instance, consider a 12V, 10Ah car battery, the battery's actual capacity is 120Wh (12V x 10Ah), but it will have a capacity of 36Wh in a 3.6V laptop battery that has the same 10Ah dissipation (3.6Vx 10Ah). You can see from the example that the amount of power a car battery can hold is three times higher than a laptop battery, even though they have the same Ah.High-power batteries always have quick discharge capabilities at high drain speeds, such as power tools or applications for vehicle starter batteries, with poor energy capacity for most high-power batteries.Ⅷ ChemistryYou would have learned by this time that all the characteristics of a battery are often dependent on the chemistry involved in the battery, so when selecting the type of battery, you should be more conscious. Batteries are known as Lead Acid Batteries, Alkaline Batteries, Ni-Cad Batteries (Nickel Cadmium), Ni- MH Batteries (Nickel Metal Hydride), Li-Ion (Lithium-Ion) and LiPoly (Lithium Polymer) Batteries based on the chemistry used in the process.Ⅸ CostThe battery will be one of the costly things in the Bill of Materials (BOM) for most portable electronic devices, so it will impact the total cost of your electronic applications most of the time. Therefore, you should know your product specifications and budget and then pick the right battery for your product.Ⅹ Shelf LifeNot all batteries are used directly after development, but they remain on the shelf for a long time before they are used. A battery's shelf life informs you how long it is possible to keep a battery unused. In primary batteries, the shelf life is largely known as a reality only because the secondary batteries can be recharged once they are used. The battery could sit idle there for years, for example, in a fire alarm siren device, until it detects a fire and activates the alarm. The battery maintains its output even if it is left unused for a long time, so care should be taken.Ⅺ How to Choose a BatteryNow that we've looked at the criteria that you should consider before selecting the battery for a portable electronic application, let's look at the common battery selection cases. Bear in mind that these are just tips and not difficult written guidelines.• You can use lead-acid batteries for items that consume more electricity, including projectors, large sound systems, and motorized projects. You can go for 'Sea deep cycle' batteries if you're going to have heavy battery use.• You can go for the lithium coin cells or small lithium polymer cells if your electronics need to be very small, about an inch on either side.• If you are going to manufacture the part, use inexpensive alkaline batteries of common sizes in large quantities. So the client considers it easy to replace them.• If you want the product to be user-serviceable, the battery can be adjusted by the customers themselves for batteries of 9V or AA capacity.• Use 3 Alkaline (4.5V) or 4NiMH (4.8V) cells if the circuit needs an input of approximately 5V.• Use a battery holder from your local shop to build a rechargeable battery pack and stick it with NiMH batteries and then begin recharging your battery.• If you want to replace any of the rechargeable batteries with your alkaline battery, test your system to make sure it will work at a lower voltage without any problems.• Always use a high-quality charger with sensors to ensure proper charging and trickle charging if you want your battery to have a longer life span since using a cheap charger would destroy your cells in the battery pack.How To Buy the Right Battery for Your CarⅫ FAQ1. How do I choose a battery?Factors to be considered while choosing a BatteryRechargeable / Non-Rechargeable batteriesAvailability of SpaceSystem Operating VoltageOperating TemperatureCapacity of the battery - Power & EnergyBattery ChemistryCost of Battery 2. What size battery does my car take?Your car's battery group size can be found in the battery section of the owner's manual. If you no longer have access to your original owner's manual, you may also consult the reference guides provided by battery retailers to determine the appropriate battery group size for your car. 3. How many Ah battery do I need for home?The battery you need will have to be powerful enough to provide the required power for at least 2 hours. As battery voltage is generally taken at 12 Volts, here is how you calculate the battery capacity. So, a battery with capacity equal to or higher than 140 Ah will suffice for your home. 4. How do I choose the right battery?To get the right battery power for your vehicle, you need to consider the cold cranking amps (CCA) and reserve capacity (RC). Cranking amps is the measure of your battery's starting power and should always match the standard requirements of your vehicle. Check the owner's manual for these specifications. 5. What brand of car battery lasts the longest?Best Rated Car Batteries for Long Lasting Performance 2020Optima RedTopExide Edge AGM Sealed BatteryOdyssey PC680ACDelco 94RAGM Professional

IntroductionIn electronics, current sense amplifiers are special-purpose amplifiers that output a voltage proportional to the current flowing in a power rail. They are often referred to as current shunt amplifiers because they use a shunt resistor in the power rail that provides a small voltage drop when current flows through the resistor. These devices are designed to handle common-mode voltages that can exceed their own supply voltage. The working principle of a current sensing amplifier is based on Ohm's law (V = I × R), where the voltage drop across the sense resistor is converted and amplified to a measurable output voltage by the current sense amplifier.Ⅰ Current Sense Amplifier Overview1.1 What is a Current Sense Amplifier?Current sense amplifiers are designed for the specific purpose of amplifying very small sensed voltages across a shunt resistor, typically within a range of 10 to 100 mV. These amplifiers are optimized for DC precision (e.g., low input offset voltage, typically less than 50 µV) and high common-mode rejection ratio (CMRR). Current sensing amplifiers can measure current flowing in a single direction (unidirectional) or in both directions through the sensing resistor. When an amplifier is capable of detecting current flow in both directions, it is called a bidirectional current sensing amplifier. Modern current sense amplifiers also feature enhanced bandwidth (up to several MHz), low quiescent current (as low as 50 µA), and integrated protection features such as overcurrent detection and alert outputs.1.2 Common-Mode Voltage and CMRRCommon-mode voltage is critical for both standard amplifiers and current sense amplifiers. The common-mode voltage refers to the average voltage applied to the inputs of the amplifier. This parameter is crucial because the amplifier has a limited ability to distinguish and differentiate signals depending on the common-mode voltage level. A standard op-amp's input range is typically insufficient for precision current sensing operations. In current sense amplifiers, the common-mode voltage range often extends well beyond the actual supply voltage of the amplifier. For example, modern current sense amplifiers can achieve supply operating voltage ranges from -4 V to +80 V, with some specialized devices supporting ranges up to +120 V or even higher for automotive and industrial applications.Op-Amp CMRR (Common Mode Rejection Ratio) ExplainedThe CMRR (common-mode rejection ratio) is the ratio of differential gain to common-mode gain, typically expressed in decibels (dB). For an ideal op-amp, the CMRR is infinite, but in real circuits, it typically ranges from 80 to 120 dB for high-performance current sense amplifiers. A high CMRR means that the amplifier can effectively reject common-mode signals while accurately amplifying the differential signal. For a current sense amplifier, high CMRR is essential because it determines how well the amplifier can measure small differential voltages in the presence of large common-mode voltages. Modern current sense amplifiers achieve CMRR values exceeding 100 dB, enabling them to sense tiny voltage drops across shunt resistors even when the common-mode voltage is several orders of magnitude larger. The high CMRR also helps eliminate noise on the current sense lines, improving measurement accuracy and system reliability.1.3 Main Types of Current Sense AmplifiersHigh-side AmplifiersThe current is measured between the supply rail and the load. The DC voltage applied to the input pins can be much higher than the amplifier's power supply voltage. High-side sensing is preferred in applications requiring ground fault detection and load diagnostics.Low-side AmplifiersThe current is measured between the load and ground. The voltage applied to the input pins is close to ground potential. Low-side sensing is simpler to implement but can interfere with ground reference integrity.Bidirectional AmplifiersThese amplifiers can measure current flow in both directions, making them ideal for battery monitoring, motor control, and applications with regenerative braking.Integrated Current Sense Amplifiers with ADCModern devices integrate analog-to-digital converters (ADC) and digital interfaces (I²C, SPI) for direct microcontroller communication, simplifying system design.Figure 1. High-side Current Sensing AmplifierⅡ Current Sense Amplifiers vs Common AmplifiersCurrent sense amplifiers and common operational amplifiers have different specifications and are designed for specific purposes. Standard operational amplifiers typically cannot amplify very small differential voltages in the presence of large common-mode voltages and have relatively low CMRR (typically 80-90 dB). In contrast, precision current sense amplifiers can detect and amplify very small voltage drops (as low as a few millivolts) while maintaining high CMRR (100-120 dB or higher).For normal operational amplifiers, the input voltage must remain between the power supply rails (VCC and VEE), and the amplifiers can only operate on input signals within this range. In a standard amplifier, applying an external voltage beyond the power rails to the input pins will activate internal ESD protection diodes, potentially causing large currents to flow and damaging the device.However, current sense amplifiers are designed to handle input voltages that far exceed their supply voltage. For example, an amplifier powered by 3.3V or 5V can safely measure voltages on power rails operating at 12V, 24V, 48V, or even higher. These amplifiers use specialized input architectures and protection circuits that allow them to operate with high common-mode voltages. When the common-mode input voltage exceeds VCC, the amplifier employs advanced circuit techniques to maintain accurate measurements without damage. Some modern current sense amplifiers also feature integrated overcurrent detection, alert outputs, and enhanced EMI/RFI rejection for robust performance in noisy industrial and automotive environments. Ⅲ How to Design a Circuit Using Current Sense AmplifiersConsider a design example with a 12V, 1A power rail where high-precision current sensing is required. Current sense amplifiers provide an ideal solution for this application. However, proper component selection is critical for optimal performance.For this application, select a current sense amplifier rated for at least 12V common-mode voltage with sufficient bandwidth for the application (typically 100 kHz to 1 MHz for DC and low-frequency AC measurements). Choose between high-side and low-side sensing based on system requirements. High-side current sensing is preferred for detecting fault or short-circuit conditions while maintaining ground integrity. Low-side current sensing offers simpler implementation but disrupts the ground reference path.The LT6108 (now part of Analog Devices) is an excellent choice for this application. This amplifier features a wide input common-mode voltage range (-0.3V to +60V), high gain accuracy, and low offset voltage. The device can operate with supply voltages from 2.9V to 60V, making it suitable for both 12V and lower voltage control circuits. Key specifications include: input offset voltage of 50 µV (typical), CMRR of 125 dB (minimum), and bandwidth of 500 kHz.Figure 2. LT6108 Circuit for Fault Protection with Fast Latching Load DisconnectThe circuit above demonstrates a practical implementation using the LT6108. A 1-ohm sense resistor creates a voltage drop proportional to the load current (1V drop at 1A). The IRF9640 P-channel MOSFET serves as the switching element, while the 2N2222 NPN transistor (note: 2N2700 in the original text appears to be a typo) provides the control function. The amplifier output can trigger the switching MOSFET to disconnect the load when current exceeds a preset threshold. In this configuration, the trip point is set at 250 mA. The circuit will open when current exceeds this limit, providing overcurrent protection. For different current thresholds (e.g., 1A), adjust the voltage divider network at the comparator input. The VOUT pin provides a voltage proportional to the sensed current, enabling real-time current monitoring. This circuit topology can be adapted using other current sense amplifiers with appropriate input voltage ranges. For higher voltage applications (24V, 48V), select amplifiers with extended common-mode voltage ranges, such as the INA240 (up to 80V) or MAX40080 (up to 60V).Design Considerations:Sense Resistor Selection: Choose a value that provides adequate voltage drop (typically 50-100 mV at full scale) while minimizing power dissipation. For 1A measurement, resistor values between 0.05Ω and 0.1Ω are common.PCB Layout: Use Kelvin connections to the sense resistor to eliminate errors from trace resistance. Keep traces short and symmetric to minimize offset errors.Filtering: Add input filtering capacitors (typically 0.1 µF ceramic) close to the amplifier inputs to reduce noise and improve stability.Gain Setting: Many current sense amplifiers offer programmable gain through external resistors, allowing optimization for specific current ranges. Ⅳ Common Applications of Current Sensing ICs4.1 Low-side Current Sense ICLow-side current sensing places the shunt resistor between the load and ground. This configuration measures current by monitoring the voltage drop across the sense resistor in the ground return path. The diagrams below demonstrate low-side measurement circuits.Practical implementations include using the INA181 current sense amplifier with its output connected to an ADC (Analog-to-Digital Converter) for digital processing. Another approach employs the AD8202 current sense amplifier from Analog Devices for sensing current through inductive loads. Modern alternatives include the INA190 series and MAX9938, which offer enhanced precision and lower power consumption.1) AdvantagesLow-side current measurement offers several benefits. The configuration is straightforward to implement because the common-mode voltage remains close to ground potential. Standard operational amplifiers or simple differential amplifiers can be used since high common-mode rejection is not critical. The low common-mode voltage simplifies circuit design and reduces component costs. Additionally, low-side sensing typically provides better noise immunity in the measurement path.2) DisadvantagesThe primary limitation of low-side current measurement is the disruption of the ground reference. Placing the shunt resistor in series with the ground path means the load no longer has a direct connection to system ground. This can cause ground bounce issues, interfere with proper operation of the load, and make it impossible to detect ground faults or short circuits to ground. Additionally, low-side sensing cannot detect leakage currents or faults that bypass the sense resistor. For these reasons, high-side sensing is often preferred in safety-critical applications.4.2 High-side Current Sense ICUnlike low-side current sensing, high-side current sensing places the shunt resistor between the positive power supply and the load. This configuration preserves ground integrity while enabling current measurement. The circuits shown below illustrate high-side current sensing implementations.Practical examples include the TI INA240, which provides analog output or integrated comparators for overcurrent detection. Some variants offer digital output via I²C interface for direct microcontroller communication. The Linear Technology LT6100 (now Analog Devices) demonstrates high-side current sensing with a fused load for enhanced protection. Modern alternatives include the INA226 (with integrated 16-bit ADC and I²C interface), MAX40080 (with integrated 12-bit ADC), and INA3221 (triple-channel monitor for multi-rail systems).Figure 3. TI INA240 in Circuit1) AdvantagesHigh-side current measurement offers significant advantages over low-side sensing. First, it maintains ground integrity, ensuring the load has a solid ground reference. This prevents ground bounce and interference issues. Second, it enables detection of all fault conditions, including short circuits to ground, since all current must flow through the sense resistor. Third, high-side sensing allows accurate measurement of the actual load current without ground path interference. Fourth, it provides better system diagnostics and fault isolation capabilities. Finally, high-side sensing is essential for battery monitoring applications where the negative terminal is grounded.2) DisadvantagesThe primary challenge of high-side current sensing is the requirement for high common-mode rejection. The small differential voltage (typically 50-100 mV) across the shunt resistor sits on top of a large common-mode voltage equal to the supply rail voltage. This requires specialized amplifiers with high CMRR (>100 dB) and wide common-mode input ranges. Additionally, high-side sensing circuits are typically more complex and expensive than low-side alternatives. However, advances in integrated circuit technology have made high-side current sense amplifiers increasingly affordable and easy to implement.4.3 Bidirectional Current Sense ICBidirectional current sense circuits use a single shunt resistor but require amplifiers capable of detecting current flow in both directions. These circuits are essential for applications such as battery charge/discharge monitoring, motor control with regenerative braking, and power management systems with bidirectional power flow.Several architectures enable bidirectional current sensing. One approach uses two current sense amplifiers (such as the INA300) connected in a configuration where each amplifier detects current flow in one direction. The circuit requires reverse polarity protection and switching logic to select the appropriate amplifier output based on current direction.A more elegant solution uses integrated bidirectional current sense amplifiers such as the INA240, INA180, or MAX40080. These devices use a reference voltage (typically mid-supply or an external reference) as the zero-current point. When current flows in one direction, the output voltage rises above the reference; when current reverses, the output falls below the reference. The differential output voltage is proportional to current magnitude, while the polarity indicates current direction.Modern bidirectional amplifiers like the INA226 and INA3221 integrate ADCs and digital interfaces, providing signed current measurements directly to microcontrollers. These devices simplify system design by eliminating external ADCs and reference voltage circuits. For high-precision applications, devices like the MAX40080 offer 12-bit resolution with ±0.1% accuracy across the full bidirectional range.4.4 Isolated Current Sense ICIsolated current sensing techniques provide galvanic isolation between the current measurement circuit and the control electronics. This is essential for high-voltage applications, safety-critical systems, and situations requiring ground loop elimination. Several isolation methods are available:Current Transformer (CT) Isolation: Uses magnetic coupling through a transformer core. The primary winding carries the measured current, inducing a proportional voltage in the secondary winding. This method is limited to AC current measurement and provides excellent isolation (typically >4 kV).Hall Effect Sensors: Measure the magnetic field generated by current flow through a conductor. Hall effect sensors can measure both DC and AC currents and provide good isolation. Examples include the ACS712, ACS724, and TMCS1100 series.Isolated Amplifiers: Use capacitive or magnetic isolation to transmit the measurement signal across an isolation barrier. Examples include the AMC1200 (capacitive isolation), Si8920 (magnetic isolation), and ACPL-C87A (optical isolation). These devices typically provide 3-5 kV isolation and can measure both DC and AC currents.Rogowski Coils: Air-core coils that measure the rate of change of current (di/dt). These are ideal for high-frequency AC current measurement and provide inherent isolation.Isolated current sensing is mandatory in applications such as motor drives, solar inverters, electric vehicle charging systems, and industrial power monitoring where high voltages and safety requirements necessitate galvanic isolation between measurement and control circuits.Figure 4. Low-side Current Sensing CircuitⅤ Key Specifications and Selection CriteriaWhen selecting a current sense amplifier, consider the following critical specifications:Common-Mode Voltage Range: Must exceed the maximum voltage on the power rail being monitored. Include margin for transients and voltage spikes.Input Offset Voltage: Determines minimum detectable current. Lower offset voltage (typically <50 µV) enables accurate measurement of small currents.CMRR: Higher values (>100 dB) provide better rejection of common-mode noise and more accurate differential measurements.Bandwidth: Must be sufficient for the application. DC to 100 kHz for most power monitoring; 1 MHz or higher for motor control and fast transient detection.Gain Options: Fixed or programmable gain allows optimization for specific current ranges.Supply Voltage: Must be compatible with system power rails. Many devices operate from 2.7V to 5.5V for easy integration with digital systems.Quiescent Current: Important for battery-powered applications. Modern devices offer quiescent currents as low as 50 µA.Package and Size: SOT-23, SOIC, and DFN packages are common. Smaller packages reduce PCB footprint but may have thermal limitations.Integrated Features: Some devices include comparators, ADCs, digital interfaces (I²C, SPI), alert outputs, and overcurrent protection.Temperature Range and Accuracy: Industrial (-40°C to +125°C) and automotive (-40°C to +150°C) grades are available. Temperature drift should be <2 µV/°C for precision applications.Ⅵ Emerging Trends and Future DevelopmentsThe current sense amplifier market continues to evolve with several notable trends:Higher Integration: Modern devices integrate ADCs, digital interfaces, voltage monitors, and power calculation engines on a single chip, reducing component count and system cost.Wider Voltage Ranges: New amplifiers support common-mode voltages up to 120V or higher, enabling direct monitoring of high-voltage rails without external attenuation.Lower Power Consumption: Shutdown modes and ultra-low quiescent current (<50 µA) enable use in battery-powered IoT devices and energy harvesting applications.Enhanced Accuracy: Improved manufacturing processes deliver offset voltages below 25 µV and gain errors below 0.1%, enabling precision measurements with smaller sense resistors and lower power loss.Automotive Qualification: AEC-Q100 qualified devices for electric vehicles, battery management systems, and 48V automotive systems.Digital Configurability: Software-programmable gain, filtering, and alert thresholds enable flexible, adaptive current monitoring systems.Multi-Channel Integration: Devices like the INA3221 integrate multiple current sense channels for simultaneous monitoring of multiple power rails.Ⅶ ConclusionAs an essential component of modern electronics, current sense amplifiers provide high-precision, flexible solutions for a wide array of applications including automotive systems, power management, battery monitoring, motor control, and industrial automation. Devices like the INA280, INA226, MAX40080, and LT6108 offer high-precision current measurement capabilities by accurately sensing voltage drops across shunt resistors. With diverse circuit requirements, a broad range of current sense amplifiers are available, including high-voltage, high-resolution, bidirectional, and isolated variants. The continued evolution of current sense amplifier technology—featuring higher integration, wider voltage ranges, lower power consumption, and enhanced digital connectivity—ensures these devices will remain critical components in next-generation power management and monitoring systems. When selecting a current sense amplifier, carefully consider application requirements including voltage range, accuracy, bandwidth, power consumption, and integration features to ensure optimal performance and system reliability. Frequently Asked Questions about Current Sense Amplifier Circuits1. What is a current sense amplifier?Current sense amplifiers (also called current shunt amplifiers) are special-purpose amplifiers that output a voltage proportional to the current flowing in a power rail. They utilize a "current-sense resistor" (shunt resistor) to convert the load current in the power rail to a small voltage, which is then amplified by the current sense amplifier. The currents in the power rail can range from milliamps to 20 A or more, requiring the current-sense resistor to be typically in the range of 1 mΩ to 100 mΩ. These amplifiers are specifically designed to handle high common-mode voltages while accurately measuring small differential voltages. 2. How does a current sense amplifier work?Current sense amplifiers work by measuring the small voltage drop across a shunt resistor placed in series with the load current. According to Ohm's law (V = I × R), the voltage drop is directly proportional to the current. The amplifier's differential inputs measure this voltage drop while rejecting the large common-mode voltage present on the power rail. The amplifier then amplifies the differential signal to produce an output voltage that can be easily measured by ADCs or comparators. Unlike normal differential amplifiers that are powered between two power supply rails (VCC and VEE) and can only handle signals between these rails, current sense amplifiers use specialized input stages that can tolerate input voltages far exceeding their supply voltage without activating ESD protection diodes or causing damage. 3. What are the main types of current sense amplifiers?The main types of current sense amplifiers include:High-Side Current Sense: Measures current between the power supply and load, maintaining ground integrity.Low-Side Current Sense: Measures current between the load and ground, offering simpler implementation.Bidirectional Current Sense: Measures current flow in both directions, essential for battery monitoring and regenerative systems.Isolated Current Sense: Provides galvanic isolation using magnetic, capacitive, or optical coupling for high-voltage and safety-critical applications. 4. What is the main purpose of a current sense amplifier?The main purpose of a current sense amplifier is to accurately measure current flow in power rails by amplifying the small voltage drop across a shunt resistor. These amplifiers can detect and amplify very small voltages, typically in the 10 to 100 mV range, while rejecting large common-mode voltages. Applications include power management, battery monitoring, motor control, overcurrent protection, system diagnostics, and energy measurement. Current sense amplifiers enable precise current monitoring for efficiency optimization, fault detection, and system protection. They can measure current flowing in a single direction (unidirectional) or in both directions (bidirectional) through the sense resistor, depending on the application requirements. 5. What is the difference between a voltage amplifier and a current sense amplifier?While both are amplifiers, they serve different purposes and have distinct specifications. Standard voltage amplifiers (operational amplifiers) are general-purpose devices designed to amplify signals within their power supply rails. They typically have moderate CMRR (80-90 dB), input voltage ranges limited to their supply voltages, and are not optimized for measuring very small differential voltages in the presence of large common-mode voltages.Current sense amplifiers, in contrast, are specialized devices optimized for measuring small voltage drops across shunt resistors. They feature very high CMRR (100-120 dB or higher), ultra-low input offset voltage (<50 µV), and the ability to handle common-mode voltages far exceeding their supply voltage. For example, a current sense amplifier powered by 3.3V can safely measure voltages on a 48V power rail. Current sense amplifiers use specialized input architectures that prevent ESD protection diodes from conducting when input voltages exceed supply rails, enabling them to operate in high-voltage environments. They are specifically designed for DC precision, high common-mode rejection, and wide common-mode voltage ranges—characteristics essential for accurate current measurement in power management applications. 6. How do I select the right shunt resistor value?Shunt resistor selection involves balancing several factors: voltage drop, power dissipation, and measurement accuracy. The voltage drop should be large enough for accurate measurement (typically 50-100 mV at full-scale current) but small enough to minimize power loss. Use the formula R = V / I, where V is the desired voltage drop and I is the maximum current. For example, for 1A measurement with 50 mV drop: R = 0.05V / 1A = 0.05Ω (50 mΩ). Power dissipation is calculated as P = I² × R. For 1A through 50 mΩ: P = 1² × 0.05 = 0.05W (50 mW). Select a resistor with adequate power rating (typically 2-4× calculated power) and low temperature coefficient (<50 ppm/°C) for stable measurements. Consider resistor tolerance (typically 1% or better) as it directly affects measurement accuracy. 7. What are the key advantages of high-side vs. low-side current sensing?High-side sensing places the shunt resistor between the power supply and load, maintaining ground integrity and enabling detection of all fault conditions including ground shorts. It provides better system diagnostics but requires amplifiers with high CMRR and wide common-mode voltage range. Low-side sensing places the shunt resistor between load and ground, offering simpler implementation and lower cost since common-mode voltage is near ground. However, it disrupts ground reference and cannot detect ground faults. High-side sensing is preferred for safety-critical applications, battery monitoring, and systems requiring fault detection, while low-side sensing is suitable for cost-sensitive applications where ground disruption is acceptable. 8. Can current sense amplifiers measure AC current?Yes, many current sense amplifiers can measure AC current, provided their bandwidth is sufficient for the frequency of interest. The amplifier's bandwidth must be at least 10× the highest frequency component of the AC signal for accurate measurement. For example, measuring 60 Hz AC requires minimum 600 Hz bandwidth. Most modern current sense amplifiers offer bandwidths from 100 kHz to several MHz. For AC-only measurements (where DC component is not needed), current transformers or Rogowski coils provide better performance. For combined DC and AC measurement (such as motor current with PWM ripple), use a current sense amplifier with adequate bandwidth and consider adding filtering to reduce high-frequency noise while preserving the signals of interest.