ABSTRACT
Such amplifiers are no use when we need to amplify an audio signal. The waveforms are complicated. When we amplify them, we must maintain their shape as exactly as possible. The aim of the audio amplifier is to produce a varying output voltage that is an exact copy of the input varying voltage, except that the voltages of the output signal are much larger. We turn signal VIN into signal VOUT:
The voltage gain of an amplifier is given by: GV = vOUT/vIN
where vOUT and vIN are the output and input voltages at any instant. An amplifier may also have current gain, defined in a similar way. Putting these two gains together, and remembering that P = IV, we can see that an amplifier increases the power of a signal.
