Automatic Gain Control (AGC)
16 Dec, 2019 by
Automatic Gain Control is employed in CCTV cameras in an attempt to keep the output signal at or near the specified one volt peak to peak (written 1Vp-p). The video signal output is sampled and fed back into the video amplifier as a reference to maintain the recommended one volt output signal. The AGC circuit in most modern day CCTV cameras with auto-iris lenses only comes into play after the lens iris is fully open. Some AGC circuits can amplify the video signal as much as 32 times but with every increase in amplification more video noise is introduced into the picture. Video noise is seen as graininess, blotchiness or distortion. If a camera’s menu has AGC settings as an option choose the lowest amount of AGC gain to give a usable picture during the time of lowest light.