LIKSTROEMSKOMPENSERAD SIGNALFOERSTAERKNINGSREGLERING

摘要

The DC output level of a video signal amplifier is compensated to remain constant as the amplifier is gain controlled in response to a gain control voltage supplied from a gain control circuit which also supplies a DC compensation voltage to the amplifier. The DC compensation is preserved by means of an additional network which senses the DC bias of both the amplifier and the gain control circuit, and corrects a deviation of the amplifier bias and the gain control circuit bias from a prescribed mutual relationship. The sensed DC bias of the gain control circuit is also used to establish a black reference level for the video signal.