Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers, which are DC-coupled high-gain electronic voltage amplifiers with a differential input and, usually, a single-ended output.

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Signal Generator, DC Offset, Impedance into an open load...workarounds?

https://www.youtube.com/watch?v=WfC0h8XhA4w MHS5200A Function Generator Review and Teardown I have the signal generator referenced in this video. As the video says, its output impedance is specified ...
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3 answers
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What type of op-amp configuration is this from a PLL circuit?

Can someone help me to understand this attached op-amp model? We are using it in an HMC3716 PLL circuit. We don't know how it works, exactly. Is it an integrator or a differentiator?
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Clamping techniques for ADC (low source impedance)

The following diagram shows an inverting high pass filter (2nd order) feeding an ADC. The DC bias of the opamp is 5.6V, which is too high for the ADC. The ADC would ideally receive the signal at ...
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How to estimate the DC error for this input and opamp?

I need to amplify a 0 to 2.5 V range DAC output to obtain a -5 to +5 V range final output and I have some of these opamps to use. In my case the DAC output to be amplified looks as follows: Looking ...
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How would I have to modify this headphone amp circuit to increase the output power of one channel?

I'm currently trying to repair an old Sony TCD-D7 DAT-Walkman. It suffers from unbalanced audio output. The right channel is much quieter than the left one during playback. The headphone amplifier ...
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  • 401
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2 answers
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Twin-T notch filter with high input impedance and low output impedance using one op-amp

I have a very space and power constrained application, where I want to apply a twin-T notch filtering to an audio signal and add a little gain of about ~10x. The following filter section has the ...
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4 votes
3 answers
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TL072P Opamp behaviour

After noticing a strange behaviour from a TL072P Opamp in a circuit I was building, I decided to test my stock, coming from two different batches, side to side. I am getting confusing results when ...
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Photodiode amplification circuit

I'm going to build photodiode amplification circuit which is then connected to ADS1115 controlled by Raspberry Pi. The operational amplifier I wanted to use is TLE2072CP. The idea is to measure ...
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4 answers
369 views

How is the input offset voltage a function of common mode voltage?

I don't know about the internals of a opamps, but is it possible to explain how a change in common mode voltage changes input offset voltage Voff? I'm asking because when the signal Vin is fed to the ...
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555 timer charge pump with feedback

In the circuit I am working on there is a requirement to create 30V DC source for a very light load (couple of mA max). I am aware that there a specialized ICs that can do that but I would like to ...
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2 votes
2 answers
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High output impedance piezo guitar pickup is better attenuated by a shunt capacitor than an inverting opamp attenuation circuit

The circuit below is meant to attenuate a high output and high output impedance piezo electric guitar bridge pickup -7 dbV. The circuit models both the pickup output impedance and load of the cable ...
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How to apply a formula on an operational amplifier? [closed]

So im solving problems like this(image) for a homework. But I got stuck on this one, and don't really know how to solve it. If anyone can help, I would be glad. The goal here is to know "the ...
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How to practically find the amplitude of a high frequency signal?

I had initially planned to use a standard peak detector circuit with an op amp of a much lower bandwidth than the signal I want to measure - my assumption was that given a high enough time domain the ...
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4 answers
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Why can't I directly measure the voltage drop on the feedback capacitor in a charge-sensitive amplifier?

The gain of a charge-sensitive amplifier (CSA) is Vo/Qi~1/Cf, where Vo is the output voltage, Qi is input charge, and Cf is the feedback capacitor. Why can't I get rid of the whole op-amp part of the ...
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How do I interface a low power controller with a higher power load?

I am not an electrical engineer (rather a photonics engineer), so I am looking for some direction on how to attack an issue I have. Basically, I need to drive a 150 Ω load with a computerized ...
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2 votes
1 answer
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Op Amp Error Calculation

I am attempting to calculate the total error in an op amp (OPA2333 to be specific) that is used in a voltage sensing circuit. If I use the OPA2333 model in my SPICE circuit, are the errors already ...
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pH-4502C pH module - Deriving the NTC resistance value through a Differential Amplifier

I recently purchased a pH-4502C pH module online and started playing with it and figuring out over the past week. I've found the circuit online and then checked the components and probed it to make ...
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How are formulas for "in the loop compensation" of capacitive load derived?

I tried to understand https://www.analog.com/media/en/analog-dialogue/volume-38/number-2/articles/techniques-to-avoid-instability-capacitive-loading.pdf The feedback circuit is as follows: so I have ...
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How to implement unity gain buffer with long-tailed pair?

I read that a unity gain buffer can be implemented with an op-amp like in this circuit: I also read that a long-tailed pair as an op-amp (this might be the wrong part). So according to the buffer ...
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3 votes
4 answers
146 views

Why doesn't compensation capacitance add additional phase for OpAmp?

The following image depicts the transfer function of an compensated against an uncompensated OpAmp. If the internal Miller-compensation capacitor results in an additional pole at low frequency I ...
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LM748 uses positive rail as an input on a 1980's UK sound effect generator. Is this an old trick that I've never seen?

TP9 is a +/-15V signal from a VCO. The signal to the base of Q7 is 0 - 10V from another card that is presumed to be basically DC. The multiplier AR11 has a sound coming from an LFSR circuit on another ...
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In-Amp Common Mode Rejection With Unbalanced Device Impedance

I am using an instrumentation amplifier (AD8220) to interface a pH probe. The pH probe produces a +/-414mV signal with large output impedance (>100MOhm). AD8220 has very low input bias current (~...
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4 answers
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Op-amp boost pedal tonal noise

I am working on a boost pedal, but I can't seem to find the cause of a humming noise in the circuit. I tried bigger caps for C5 and C6, but it didn't solve the issue. For power I use an 18V model ...
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In a DC voltage sensing circuit, what's the need for capacitors on input and output?

This circuit uses a voltage divider to lower the voltage, and then uses an op-amp as a buffer (with some gain). If the input signal is always DC, why do I need these capacitors? The way I understand ...
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2 votes
2 answers
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Are op-amp (LM324) power rails physically connected to their input terminals?

I have an AC voltage sensing circuit which uses an op-amp circuit with a LOC110 linear optical isolator. The left-side op-amp is powered by a supply voltage derived from a different AC source (an ...
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2 votes
2 answers
678 views

Sine to bipolar sine

I have a circuit that outputs a positive sine wave with an amplitude from ~0.6V to 0V. The peak values can vary from 0.6V down to 0V. An example of two possible waveforms are shown in the image below: ...
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Looking for OPA2227 SPICE model

I did not find this op-amp in LTspice and also I could not find a library for it on Google. Can someone help me find it?
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Potentiometer action in an audio mixer

I found these schematics for an audio mixer. I reproduce the mainpart of the schematics. A first stage of input buffers before each in line consisting of an opamp is not reproduced. I am only ...
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3 answers
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My Wien bridge oscillator doesn't work, what could the problem be?

I suspect I am making a probe connection mistake, but couldn't figure it out. The circuit works fine in LTSpice but I don't get anything in a real experiment. What might be the problem?
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1 vote
6 answers
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Why is a non inverting unity gain opamp's output not zero all the time?

In this circuit: simulate this circuit – Schematic created using CircuitLab The input is continually summing with its negative through negative feedback, so it must become zero on the output. ...
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3 votes
1 answer
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How to measure voltage with a floating supply?

In the example below, ground of a dual supply is referenced to +Vout. Assuming we have a MCU connected to VCC and +Vout, if we then try to measure the voltage at +Vout with the ADC, we're basically ...
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5 votes
5 answers
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Why does this op amp input stage have single ended output?

Looking at the internal diagram of LM324: I see that the output of the the input stage, which is a differential pair, is single ended rather than being a differential output. How does then this input ...
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2 answers
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Offset amplifier's input to prevent opamp clipping

We can do this: With AC coupling and biasing op-amp input. Summing using buffered resistor Using sum and difference inherited in OpAmp and sum signal with desirably created virtual ground 1 is good ...
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-1 votes
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Unity gain non-inverting op-amp do not have reference signal, why?

As you know, asimple amplifier with input to its + and out shorted to - its output will follow its input almost exactly. Where is it's input reference input? How I can connect it to the desired ...
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7 votes
4 answers
404 views

Is my summary of parasitic oscillation in op-amps wrong?

We were discussing negative feedback in op-amps with my community college instructor. I tried to learn ahead about the concept of parasitic oscillations in feedback circuits. I wrote a summary of what ...
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-1 votes
3 answers
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Do active filters count as amplifers?

Can we consider active filters to be amplifers? If we use the folowing active filter design, and adjust R1 and R2 correctly that the gain is set to 10 for example, does the output signal comes out ...
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5 answers
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How to decrease distortion and efficiency of this circuit?

How to achieve efficiency of more than 70% and decrease the distortion of the circuit to 0.1% in THD, without affecting my Vpp=30 with the circuit below with both in 1k and 6k frequency of Vs? Update ...
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0 votes
1 answer
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Why does an AC 230V sensor (with ~5V DC output) need an amplifier and offset voltage circuit? [closed]

I want to design a reliable, production-ready circuit for measuring the AC voltage (230V 50Hz) on the mains supply on a microcontroller. The circuit that I could come up with would involve: A ...
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1 vote
1 answer
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Pressure Transducer, Reverse and Shift Output of a differential amplifier

I am making a custom hydraulic brake for my sim racing setup. The original brake uses a potentiometer which outputs 3.3V at no brake pressure and 0V at full brake pressure. My pressure transducer, ...
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2 answers
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Amplifying a DC guitar signal with an op amp

I am looking to amplify a DC signal that will range from 0 to 400mV by at around 5-10X and read it with my DAQ. I currently have a TLV271 and a UA741CP that I tried to use in a non-inverting circuit. ...
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3 votes
1 answer
165 views

Generated sound

I got these schematics from an arcade game released in 1983. These two circuits are responsible for generating two different sounds even though they look very similar. First one (sounds like a whistle)...
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1 answer
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DC voltage attenuation

I need to attenuate 0-5V to 0-1 mV. The output of simple voltage dividers (normal op amps or resistor divider) can't be distinguished from baseline noise (baseline noise is 10-20mV.) How can I ...
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Are there any ways to increasing the gain and ICMRs to this opamp?

Here's the netlist of this CMOS opamp schematics. ...
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1 vote
1 answer
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Substract Offset Voltages of Operational Amplifiers

In the circuit below the two LM324 Operational Amplifiers are from the same IC. The Offset Voltage of each OpAmp is specified to be up to 7 mV at 25 ºC. The Offset Voltage mismatch is not specified or ...
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Transmit changing shunt resistor voltage value using analog optocoupler

I would like to use the IL300 to transmit the voltage of a shunt-resistor. The voltage value of the shunt changes between 0 up to 1 volt in 1ms depending on the load. On the receiving side of the ...
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0 votes
1 answer
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Designing a two stage push-pull class B audio amplifier

I am designing a two stage push-pull class B audio amplifier with s 2N4401 used as my pte-amplifier stage and TIP31C & TIP32C as my push-pull stage where my RL is a 10W speaker. I am trying to set ...
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1 vote
2 answers
169 views

Op-Amp complex impedance

I am having some trouble understanding the background of this question. I think they are saying that as you sweep the frequency of Vin, the impedance Zin seen will be different as you pass through the ...
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1 vote
1 answer
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Can we use an integrator circuit as a Hilbert transformer?

I want to know about the hardware implementation of Hilbert transform. Can an integrator circuit be used to introduce a -90° phase shift to the input signal?
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3 votes
4 answers
330 views

concatenating first order high pass filters

I have the following circuit, which is an active high pass filter with the knee frequency \$ f_{-3dB} = \frac{1}{2\pi RC} = 1kHz\$ I wanted to concatenate two of those systems in order to make a ...
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1 vote
1 answer
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Feedback loop gain not as expected in a differential amplifier

I am trying to build an approximate opamp with a differential amplifier and add a feedback loop to get the approximate wanted gain. I used a differential amplifier with a current source and a current ...
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