Amplification is the process of increasing the amplitude of a AC signal current or voltage such as audio signal for sound or video signal for a television picture. The amplifier allows a small input signal to control a larger amount of power in the output circuit. The output signal is a copy of the original input signal but has higher amplitude. Amplification is neccessary as in most applications, the signal is too weak to be used directly. For example, an audio output of 1mV from a microphone is not able to drive a loud speaker which requires a few volts to operate. Hence, the signal need to be amplified to a few volts before it can be fed into the loud speaker.
