What is the difference between the voltage follower circuit of the transistor and the operational amplifier?

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What is the difference between the voltage follower circuit of the transistor and the operational amplifier? [Copy link]

What is the difference between the voltage follower circuit of a transistor and an op amp? The circuit of a transistor is current driven. Is there a requirement for the input power of the transistor?

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For a voltage follower circuit composed of a single transistor, there is always a voltage between the output and the input, which is the voltage drop of the emitter junction of the transistor, which is generally a few tenths of a volt. For a follower circuit composed of an op amp, because the op amp input stage always uses a differential circuit, the voltage between the output and input of the follower circuit is very small, generally a few millivolts, or even as small as a few microvolts.