Automatic gain control

The video signal output by the camera must reach the standard level specified by the TV transmission, that is, in order to be able to output the standard video signal under different scene illumination conditions, the gain of the amplifier must be adjusted in a large range. This gain adjustment is usually done automatically by detecting the average level of the video signal. The circuit that achieves this function is called an automatic gain control circuit, or AGC circuit for short. The sensitivity of the camera with AGC function will be improved at low illumination, but the noise at this time will also be more obvious, this is because the signal and noise are amplified at the same time.