AC signal input, what will be in the output of an opamp or a transistor

In both cases it all depends on how the device, op-amp or single transistor, is biased and the configuration of the surrounding circuit.

Your question is far too vague to give a specific answer.

JimB

You should get an amplified equal AC waveform as the inputted if the circuit is properly tailored to amplify, or railed or peaked or differential or distorted or integrated if the circuit is tailored for that.

Otto_ said:

Good day, everyone.
1) If an AC signal (for example, sine) is put into an opamp (which is supplied with DC), what kind of signal (AC, DC or pulsating DC) will be in the output?
2) What would be in the case of a single transistor (I suppose, it does not matter, BJT or FET, because anyway there is a p-n junction):
AC input --> pulsating DC output (like in the case of a diode as a half-wave rectifier); pulsating DC input --> pulsating DC output?

Thank You in advance

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Hello there,

In general, op amps are usually set up to amplify AC signals and maintain the integrity of the waveform. However, there are various conditions that can prevent that. If it's say an audio amplifier, it will most likely put out an AC signal that has the same shape as the input signal.

Transistors, on the other hand, are very nonlinear and so require a carefully designed circuit to be able to reproduce an AC signal. A transistor alone will not work at all, at least a few resistors would be required.

There is a lot of thought that goes into designing a transistor amplifier like an audio amplifier. The op amp amplifiers are easier to understand. If you are interested in both types of circuits, you can ask about each type separately and you should get some good answers.