The basic components of an amplifier are an input source, an amplifying element, and an output device.The input source is typically a microphone, an electric guitar, or other sound source.
The amplifying element is typically a transistor, vacuum tube, or operational amplifier (op–amp). The output device is typically a speaker, a transistor, or an operational amplifier.
The purpose of an amplifier is to take a small signal, such as a microphone input, and amplify it to a larger, more usable signal.
This is done by increasing the current, voltage, or power of the signal. The output signal is usually larger in amplitude and has a higher power than the input signal.
Amplifiers are often used in combination with other components to create a complete sound system.