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.
9,079 questions
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Calculate the max source voltage to avoid saturation
I have this circuit
IMHO, 22k and 47k are resistors in parallel, so
$$\frac{22(47)}{47k+22}=14985.507\Omega $$
$$15+33=48k\\$$
Then you have this circuit
Since its an inverting amplifier
$$V_{o}=\...
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Input Noise Of An Op-amp
I want to detect a 200 nVrms signal at 30 kHz. For this purpose, I will build a circuit whose block diagram is shown below. First, I will take this signal and amplify it by 40 dB using a preamplifier (...
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Solve This Op-Amp Question Using KCL At Nodes
I tried to solve this question by applying KCL at the first inverting node and then applied it to the 2nd inverting node.
The answer I got is \$V_o\$ = 66V, which is not possible, and for Point B = -...
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Does op amp input impedance (significantly) vary with supply voltage?
Please refer to the following app note: https://www.ti.com/lit/pdf/sbaa374
It is a resistive circuit in front of a noninverting op amp to scale and level shift an (bipolar) input voltage.
I get the ...
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Op-amp biasing not working as intended
This is regarding the biasing of a second order Sallen-Key low pass filter. The filter seems to work fine when I use a sinusoidal input in LTSpice and produces an output centered around 1.65 V. ...
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Common mode signal definition: why use the arithmetic average of the two signals? Is it empirically motivated?
In a post I made the other day about common mode signal and op-amps, some exchange in the comments led me to note that the definition of \$V_{\text{CM}}\$ seemed rather arbitrary. The canonical ...
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Schematic for a ±9V power supply for op-amps from USB power? [closed]
The MAX232 provides roughly ±9V from USB power (~5VDC) but I believe the current it can handle would be inadequate for the 8 op-amp board I am developing.
My board has two channels: each consisting of ...
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Op-amp output distorted after adding decoupling capacitors to ±12 V power rails (and need alternative noise filter)
I’m working on a non-inverting op-amp circuit with:
AC input: 1 Vpk at 1 kHz
DC offset: 2 V in series with the AC signal
Gain: 3 V/V
±12 V power rails
There is significant simulated noise on the ...
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Circuit to combine two PWM generated sound signals
I am working on a sound synthesizer using an ATmega328. My synthesizer works for now, and has two voices. Of course I want these voices to be mixed and though I'd use an opamp for that. I have the ...
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How to protect the AC-coupled input of an opamp from transient current
I have an AC coupled opamp configured like this:
simulate this circuit – Schematic created using CircuitLab
When I connect V1 to the input, the simulation shows an spike of ~48mA that reduces to ...
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Unclear resistors in the flow sensor connection circuitry
There is a flow sensor (volume of air per unit of time) AWM92100V.
The principle of its operation:
There is a heater, there are 2 thermistors on both sides of it. The air flow cools the 1st thermistor,...
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Rectifying Audio Circuit
I am a bit confused with a circuit I've designed myself long time ago but only simulated on simulink and never built it. Now I've built it on a protoboard and I am getting some considerable deviations ...
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Singular matrix: check node error
What is the problem in my circuit? I tried changing the voltages but its no use. I made the same circuit that was working but it’s not working now. What is wrong with it? I’d be grateful for your help....
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Do these two opamp circuit have different gain?
\$\newcommand{\parallelsum}{\mathbin{/\mkern-8mu/}}\$I'm curious about the difference between these two topologies of differential amplifiers. I know that for the first one (the 5 transistor topology) ...
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Center channel extraction from stereo audio
My TV audio line level out is connected to a pair of amplified speakers. The system lacks vocal clarity and I want to add a center channel to enhance dialogues. The passive technique is in below ...
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Identify a SOT-353 IC with "AC" top marking on a Powersoft DSP board
I'm looking for assistance identifying this SOT-353 surface mount component with "AC" marked on top. This is on a Powersoft DSP board out of a Digimod audio amplifier. My understanding is ...
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Why is amplifier bandwidth defined at −3 dB?
Why is the voltage amplification factor of an amplifier or a filter generally expressed by its gain in decibels, and why is the bandwidth of this amplifier defined at −3 dB?
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How does this square root circuit work?
I am having a hard time understanding it and I'm planning to use this concept for my true RMS to DC converter.
Here is the source: https://usermanual.wiki/Document/snla140b.1643036625/view
also here (...
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Is reverse current through an op amp output a problem? Or can op amps tolerate reverse current?
I have an op amp output in series with a capacitor and a resistor which is then connected to the input of an optocoupler which triggers a "HIGH" input on my mcu input pin. I need isolation ...
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Op Amp Circuit Feedback Question
Consider the inverting op-amp circuit shown. The output voltage is given by
$$
V_{\mathrm{out}}(\omega) = -\frac{Z_2(\omega)}{Z_1(\omega)} V_{\mathrm{in}}(\omega)
$$
where
$$
Z_1(\omega) = R_1, \qquad ...
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What is the purpose of R2 in this op-amp–based voltage regulator circuit?
I am playing around with familiarizing myself more with op amps and circuits in general. I came across a circuit on a website and I am a bit confused by the placement of one of the components and I am ...
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Difficulty implementing differential output stage
I’ve developed an elliptical circuit followed by 3 op-amp stages. The final output needs to go into an LPC4370 ADC (can’t be changed), which requires a differential input (100 mV to 900 mV range). I ...
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Open-loop gain measurement in LTspice
I'm trying to find the open-loop gain of the LTC6228, after looking up on several questions on stack Exchange, I learnt that I have to auto-bias the circuit.
The answers on those questions talk about ...
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How do I derive the exact frequency formula for this integrator + non-inverting Schmitt triangle/square oscillator?
I’m trying to understand (and derive) the frequency equation for the classic triangle/square function generator made from an inverting integrator driven by a non-inverting Schmitt trigger. The ...
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Proper way to simulate op-amp phase/gain margin with input capacitance?
I would like to simulate the phase margin of an op-amp configured as a transimpedance amplifier. I am using the ADA4817. For high speed op-amps you have to be careful about parasitic capacitance to ...
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