AUTOMATIC CONTRAST CONTROL CIRCUIT

摘要

The control circuit for obtaining a sharp contrast ratio includes a pedestal level sample and hold circuit (20) for sampling and holding a video signal clamped to a pedestal level by a clamping pulse; a circuit (15) for detectingh a signal below a reference level to remove unnecessary blanking signal by blanking-out such that only the signal below the reference level is determined; a lowest value detection circuit (15) for detecting the lowest value of a image signal mean value detection circuit (25) and of the clamped video signal; a comparator circuit (10) for comparing the lowest value from the detector (15) with the image signal mean value from the detector (25) and pedestal level signal; and a variable gin amplifier (30).