Video signal AGC circuit for adjusting the sync level of a video signal

摘要

A video signal AGC circuit including an analog gain control amplifier for adjusting the level of an input analog video signal; an A-D converter for converting the output of the analog gain control amplifier to a digital video signal; a sync level detector for detecting the sync level of the digital video signal outputted from the A-D converter; a digital gain control amplifier for adjusting the level of the digital video signal outputted from the A-D converter; a first control signal generator for generating a first control signal to adjust the gain of the analog gain control amplifier on the basis of the output of the sync level detector; and a second control signal generator for generating a second control signal to adjust the gain of the digital gain control amplifier on the basis of the output of the sync level detector. In this AGC circuit, the sync level detector includes a detector for detecting the sync signal of the output of the A-D converter; a detector for detecting, on the basis of the sync signal, the pedestal data corresponding to the pedestal level; and a detector for detecting, on the basis of the sync signal, the sync tip data corresponding to the sync tip level.