Voltage or Power amplifiers

[Spectacular Butter]

Normally, when do we need to amplify voltage and when do we amplify power instead?

 

[Nigel Goodwin]

Normally, when do we need to amplify voltage and when do we amplify power instead?

Basically you amplify power when you need power, so an audio preamplifier is generally considered a voltage amplifier (as a preamplifier only needs a low power output), where as an audio output amplifier is driving a speaker, so needs to amplify the power.

There's not really any difference though, it's just the output current capability of the stage.

Even a preamplifer (or just a single transistor stage) actually provided power gain as well - simply compare the input and output impedances.