AGC is automatic gain control, which means that the gain of the amplifier circuit is automatically adjusted with the strength of the signal. The process of automatically adjusting the gain of an amplifier. Usually, the output signal level changes little with the input signal level.

For example, when a radio listens to a weak signal from a distant station, it needs a larger magnification to listen to it normally, while when it listens to a strong local signal with the same magnification, it will cause serious signal distortion, and it must be reduced to listen to it normally. It can be seen that automatic gain control is an indispensable requirement in many cases.

Extended data

When a weak signal is input, the linear amplifier circuit works to ensure the intensity of the output signal; When the input signal reaches a certain intensity, start the compression amplifier circuit to reduce the output amplitude; The AGC function can automatically control the amplitude of gain by changing the compression ratio of input and output.

The gain control method of the amplifier circuit includes: changing the DC working state of the transistor to change the current amplification coefficient β of the transistor; Inserting an electrically controlled attenuator between stages of the amplifier; An electronically controlled variable resistor is used as the amplifier load. AGC circuits are widely used in various receivers. Recorders and measuring instruments.

References:

Baidu Encyclopedia-Automatic Gain Control