Electrical – What’s the actual difference between voltage gain, current gain and power gain

amplifiergainpowerpower electronicstransistors

Why do we intend to obtain different gains at different places?
In an emitter follower for example,

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There's no voltage gain, but there's current gain and therefore it has power gain. Okay, how's that different and useful from having an voltage gain? And what's the difference between current and power gain. In power amplifiers,

Since any more voltage amplification would lead to distortion, we
amplify the power(current).

What effect does amplifying power bring with it?

Best Answer

Gain is simply output/input, for example Vout/Vin. So for an emitter follower you cannot say that "it has no gain" because it does!

An emitter follower has a voltage gain, Vout/Vin of slightly less than 1. (and this is what you mean by "it has no gain", indeed the signal voltage isn't increased).

But an emitter follower can have a current gain Iout/Iin of much more, use the right transistor and the current gain can be a factor 500.

To achieve power gain Pout/Pin we must realize that Power = Voltage x Current so if we change the Voltage and/or Current such that output power is increased, we have power gain. In the case of the emitter follower, most power gain is due to the current gain.

For a common emitter circuit, both voltage and current gain can contribute to power gain of more than one.