The linear amplifier are designed to amplify the analog signals. Analog signals are the signals the magnitude can take any value and signal can vary continuously with time.

A linear amplifier is then supposed to multiply the i/p signal by a constant to produce the o/p. This multiplying factor is greater than I and called as “gain” of the amplifier.

Block diagram

In order to magnify the input signal Vs, all the amplifiers need a source of energy. This may be provided by energy. This may be provided by a battery or a dc power supply. The dc power supply is also essential for biasing BJT.

The amplifier should contain at least one active device such as a transistor or field effect transistor (FET) or an operational amp (OP- AMP)

If a transistor is used then it should be biased in the active region.