Electrical Engineering Stack Exchange
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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.

An operational amplifier is a DC-coupled, high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.

An op-amp produces an output potential that is typically hundreds of thousands of times larger than the potential difference between its input terminals. Operational amplifiers had their origins in analog computers, where they were used to perform mathematical operations in many linear, non-linear, and frequency-dependent circuits.

The popularity of the op-amp as a building block in analog circuits is due to its versatility. By using negative feedback, the characteristics of an op-amp circuit, its gain, input and output impedance, bandwidth, etc. are determined by external components and have little dependence on temperature coefficients or engineering tolerances in the op-amp itself.

(Excerpted from Wikipedia)

Further reading

Texas Instruments application report SLOA011: Understanding operational amplifier specifications

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What is the purpose of a resistor in the feedback path of a unity gain buffer?

I often see unity-gain followers with a resistor in the feedback path. For an ideal op-amp, of course, there is no current into the input, and this resistor does nothing. What is its effect with a real op-amp, and how do I choose its value? What…
nibot
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What is the advantage of the inverting opamp circuit over non-inverting one?

Op amp circuits are designed to achieve a specific gain regardless of the differences between individual op amps. One very common circuit has a gain of -R2/R1. Here's a (corrected) schematic: Another common configuration has a gain of R2/R1+1 and…
Dov
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What's the uA741's appeal?

OK, so the uA741 is 42 years old now. For its time it may have been a great opamp; the requirements weren't as high as today, and there was far less competition. But I was wondering what's the 741's appeal today. it's slow. GBW 1MHz, slew rate…
stevenvh
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What's special about "unity-gain stable"?

As mentioned in opamp datasheets, like this one. I would think stability is a problem at higher gains, due to oscillation. What are the problems with unity-gain?
Federico Russo
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What is "offset null" in IC 741?

What is Offset null in 1st and 5th pin in IC 741 (Op-Amp)? Why it is used, though it is not used in many circuits? Give me explanation regarding the offset null! Why offset voltage was formed in IC 741?
Abishek ram R
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What is the difference between operational, differential, and instrumentation amplifiers?

RS Components lists three categories of similar amplifiers: Operational Amplifiers, Differential Amplifiers, and Instrumentation Amplifiers. I think that there should be a single section called Operational Amplifiers. Why do these three separate…
quantum231
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Subtracting two voltages using an op-amp

I'm essentially a digital guy, and am used to using a comparator to compare two voltages and give a high or low depending on their relative values. Now instead I want to subtract one voltage from another, and have the difference be available as an…
tcrosley
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Are the offset voltages in a dual/quad op amp correlated?

On a single piece of silicon on which there is more then one op amp, are the input offset voltages at all correlated, i.e. would they be expected to be same direction and similar magnitude?
crj11
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How does this inverting opamp circuit with adjustible bandwidth work?

Either my textbook author is a scoundrel or I don't have the prerequisites to understand even a simple op-amp circuit. I understand how a basic inverting amplifier works and I get how the gain falls off due to the internal RC circuit (miller…
AgentS
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caveats in rail-to-rail I/O opamps?

There are a large number of opamps in the so-called "rail-to-rail" category: these either have an input common-mode range that approaches or exceeds the power supply rails, or they have an output range that approaches the power supply rails. I'm…
Jason S
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Op-Amp input question

I'm self-taught in electronics and while I can do the digital stuff fairly readily, analog throws me for a loop. I'm looking at an audio CODEC and the reference schematic has this on the input to the ADC: I understand that C11 is there to…
Nevo
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How do the open loop voltage gain and closed loop voltage gain differ?

The closed-loop gain of op-amp is calculated by the ratio of Vout/Vin. What about the open-loop gain? How does the value of open-loop gain and closed-loop gain affect the performance of op-amp ? What is the relationship between open-loop and…
nee
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opamp without negative supply

I connected the V- pin to ground and the V+ pin to +5V. I then connected in+ to ground and in- to +5V. I expected Vout to be a low value near ground (0V) but I'm getting about +1.7V. Is this normal?
Steven Lu
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Op-amp gain bandwidth product

I've had this question for a while. Assume you have an otherwise perfect op-amp with a gain-bandwidth product of 5 MHz. You input a signal of 50mVp-p and amplify it by 10x. This limits your bandwidth to 500 kHz. Now, say you stack another op-amp on…
Thomas O
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What exactly is stopping OpAmps from reaching VCC/GND?

So I have been reading about OpAmps and also simulated a bit with Ltspice. I made a simple Integrator with an LM324 OpAmp and its getting close to the positive rail but Its not really exact. What is causing OpAmps not reaching exact positive rail…
Karl S.
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