# Tagged Questions

An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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### How to translate analog inputs at [-15,+15V] to [0,+3.3V] without ±15V rails?

Title says it all, but to provide some context: the goal here is to design a 12-channels ADC system. Input signals varies between -15 and +15V. The acquisition system will probably be a mid/large ...
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### DC Motor Power Amplifier issue

i built this DC motor power amplifier to drive the motor in both directions using an analog signal (from -1 volt to 1 volt via the potentiometer ) , the motor i use is rated for 24 volts and draws ...
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### current sense circuit simulation using TINA

I have been trying to simulate a current sense circuit with TINA a Texas instruments simulator. I need to make a current sense circuit with an INA 105 opamp and a 0.1 ohm resistor. Please help me ...
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### A difference amplifier with a non-grounded non-inverting input

My question is simple. Let's say Vin1 = 5V and Vin2 varies from 0 to 5V. What is Vout, if the non-inverting input is not connected to ground (with or without a resistor between the + input and ...
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### How to prevent floating input for this system?

I have a simple system where a motor speed is controlled by a voltage signal via a circuit. Below represents the system where A is the voltage signal device; B is the circuit and M is the motor. The ...
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### current to voltage op amp [duplicate]

In the circuit underneath, I used a LF357 op-amp. The offset of LF357 is high and I want to replace it with the LT1468 op-amp. Although the specifications of LT1468 are better than LF357, when I ...
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### OP AMP CONVERT CURRENT TO VOLTAGE

I see in a schematic , a op amp(lf357 or lf411)convert current to voltage amplifier .(current come from a loop of wire) . Now I want implement that circuit with LT1468. but not work correctly. what ...
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### For mixing two audio signals, should I run each input through an op-amp individually then sum them with a third op-amp?

I have very limited knowledge in circuitry so please forgive me in advance if I say anything that doesn't make sense. I'm designing a circuit that is going to take two audio signals, one from an ...
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### How to deal with really tiny op-amps?

Every time I order an op-amp from DigiKey the op-amp arms are waaaay too small. Too small to prototype in my circuit board, and sometimes too small to solder. Is my only option to make a custom PCB, ...
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### Looking for a low offset drift opamp [on hold]

I need an opamp for a low frequency sensing application (around 1mHz). Since the device in question may be used outside and thus subject to temperature changes (sunlight, rain, etc.). A variation in ...
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### AC Current sink with op amp and transistor

I want to create an AC load for testing high capacity battery (200Ah) using the circuit below: Can I put an AC voltage at Vin and get a AC load current through the FET? And why do they need LT1492 ...
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### Oscillation in Voltage Rectifier / Scaling Circuit

I am working on creating a circuit that will scale +/- 12v input to a unipolar 3.3v centered around 1.65v, in order to scale the kind of CV used in modular synthesis systems to work with the ADCs on ...
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### How to define supply voltage drop across transimpedance amplifier [on hold]

simulate this circuit – Schematic created using CircuitLab I am using a transimpedance amplifier with a photodiode to convert current from diode to voltage. It is a generic circuit to measure ...
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### How do I realize a transfer function with multiple zeros?

I designed a compensation function for a control system in Matlab and now I'm trying to figure out how to build it using op-amps. I thought I might be able to use a couple of Sallen-Key amplifier ...
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### Question about op amp input capacitor

Please take a look at this link about biasing input for single ended op-amp topology: http://www.analog.com/library/analogDialogue/archives/35-02/avoiding/index.html In figure 1, I notice they put a ...
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### What is the function of the diode in the image?

I am buildind a circuit like this, but I am confused about D1, is it necessary?
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### Why do I get maximum output from OpAmp

I adapted a circuit for a voltage controlled isolated resistor using a LM324 OpAmp, a Darlington NPN (MPSA14), and a Fairchild Opto-FET (H11F1). The mission is to provide a 0 - 10K isolated ...
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### Op Amp DC multiplier

Is there a circuit (that only uses op-amp and resistors) that performs multiplication between two DC input signals v1 and v2? Similar to the Summing Amplifier but with multiplication.
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### Is the input impedance of an operational amplifier (op amp) infinite or zero?

Ideally, the input impedance is infinite. But, in calculating the input resistance (Rin) of a difference amplifier, the author took the concept that the two input terminals are short circuited, which ...
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### How to select the right Operational Amplifier as an impedance converter?

I have a receiver circuit that is magnetically coupled via a parallel resonant circuit with the sender (similar to RFID but just one directional). I want to feed the signal into an ADC which has, ...
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### Why does the regulated voltage go down?

I have designed this simple analog temperature transmitter. Specifically, this is a 2-wires loop-powered transmitter. The circuit is intended to measure temperatures from -50 to 400 °C. The first ...
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### How does this temperature alarm circuit work

Casn you please help me understand how this temperature alarm circuit works? I am a bit over my head here, but I would very much like to understand this. If you would like to look at the multisim ...
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### Harmonic distortion in sub threshold 2 stage opamp

I have designed an 2 stage opamp with all MOSFETs in subthreshold region as shown in the figure below, I have gain of 48 dB, GBW of 60KHz, Slew rate of 0.014 V/us and Power dissipation of just 0.6 ...
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### Adjust output offset of a Signal

i am trying to develop a signal generator which can have sin and rectangular signals . Another requirement is to adjust offset to +-1V.Here comes the question . I have finished to adjust + offset by ...
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### iCircuit Voltage Comparator

How can I add voltage comparator LM2903M to iCircuit? I tried to find some tutorial or any other instruction but I failed. I will appreciate any help!
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### How can I simulate in PSpice the model LM13700?

Hello to everyone and apologies if this question has been asked before, but I am searching more than an hour every time before I post. I want to simulate the LM13700 Operational Transconductance ...
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### Op-Amp damage from floating input

I have an op-amp circuit that has a block of dip switches that can be used to configure the gain of the circuit. We have had an unusual failure in the circuit that appears to be related to changing ...
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### Input capacitance of a differential amplifier

This lecture (page 11) shows how to calculate input impedance of a differential amplifier. As you can see from the image below the input capacitance is calculated through the steps shown at the right....
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### How can I determine the equation for the output voltage?

This is circuit is proposed for a thermomether based on the TSP102 sensor (linear PTC). How can I determine the equation for the output voltage? My main question is about the op amp. I know that two ...
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### Inverting op amp used with low frequency oscillator

I am designing a low frequency oscillator. An image of the schematic is below. The oscillator part works fine. My intention is to scale the triangle wave at the output of U1 to +/-2.5 V by using U4....
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### Is the 555 necessary here, or can I just use an op-amp?

Context: The circuit's main input is a line-level audio signal from a computer. Every time that something loud happens in the audio, I need the solenoid to activate for about 100 ms. The first ...
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### Driving line input of a speaker from a differential amplifier, why is the output clipped?

I have a differential audio signal which I want to use to drive a single-ended device (in this case, an amplified pc desktop speaker with line level inputs) with 10kohm impedance. I have wired up a ...
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### Unity Gain Op Amp Configuration: Stability?

I'm planning to use the ADA4610 in unity gain configuration as a current buffer for a high precision (16-bit) DAC chip. The chip is labeled as being stable in the unity gain configuration. I currently ...
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### How to increase the sensitivity of this EMF detector (Arduino based)? [closed]

I built this simple circuit that I found on the web to detect electromagnetic field signals: Basically, an antenna is plugged in to both the Arduino's analog input (directly) and to the ground (...
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### Feedback and phase shift on op-amps

I understand that if an op-amp has a phase shift of 180$^{\circ}$ and a gain of >1 it will oscillate and I'm trying to get an intuitive feeling for how / why. I've read around a bit, but I don't ...
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### Op amp amplifier with capacitor [closed]

What happens when the resistors of an op amp amplifier circuit are replaced with capacitors? Or inductors? What is the frequency response of such an arrangement?
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### lm324 current can draw safely

as we all know lm 324 consist 4 op-amp now the datasheet says current limitation like 40mA. Now I want to ask that whether 40mA for each op-amp or the sum of all 4 op-amp Link to the datasheet here.
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### How to distibute power between MOSFETs and resistors in current limiter cirquit

I thinking about making some sort of not-very-big-power hi-side current+voltage limiter, using cheap china SOT-23 P-chenel MOSFET like IRF9310PBF, BSC030P03NS3G or AO4407. But in some user cases ...
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### Input offset voltage transimpedance amplifier

I am currently creating a transimpedance amplifier for a small-area photodiode that creates around 0.15mA, 0.00015A, from it's associated laser diode at it's nominal operating point. I am currently ...
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### low pass filter

I am working on a data acquisition system and i wish to get data from a pressure sensor . I have designed an analog circuit based on information i have collected which consists of an Instrumentation ...
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### Unipolar Hall current sensor signal conditioning for 5v ADC

Need help. I need to convert signal (0v to 5v) from Hall-based unipolar current sensor measuring the power line from the 84v 4kW battery pack to 5v MCU based ADC converter. Although both – the sensor ...
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### Queries regarding Digital power supply design

I was designing a 0-35v/6A power supply with keypad entry with microcontroller.The main idea is to output calculated output voltage by a 12 bit DAC and feed it to an op-amp configured as non inverting ...
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### Input impedance from RC filter to inverting and non inverting op amp

I am building a preamp for a sinusoidal current source. I have a two stage amplification process, with a bandpass RC filter in the middle. The second stage amplification is has two outputs from an ...
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### Is possible to implement this op-amp split power supply design? [closed]

Hi all, I have a op-amp charge pump circuit that could produce up to 3A 1000Hz AC current regardless of load. This current is used to test a battery (V1 in the image). The weird part is that I have ...
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### Differential Input to Single Ended Output with Fully Differential Amplifier?

I am using LT1994 Fully Differential Input/Output Amplifier for a single-input to differential output configuration with no problem. I need to use same amplifier for differential input to single-...
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### What can I do for this glucose meter circuit?

simulate this circuit – Schematic created using CircuitLab Hi guys! I am making a two-cell glucose meter. Here is may design. Of course, as you see, there are many problems that I cannot figure ...
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### low pass filter and gain calculation

I am working on a data acquisition system project . I have used SMPS power supply and two pressure sensors(-5V to +5V input) and (0-20mV o/p) my analog circuit consists of one op-amp(OP07) and one ...
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### Type J Thermocouple Signal Conditioning to 0-5V

I've been working with signal conditioning, thermocouple out specifically. I'm working with a span of 450 °C, that is, from -50 °C to 400 °C. For those values of temperatures I get, according to the ...