Video signals clamping circuit for maintaining DC level of video signals

摘要

A video signal clamping circuit capable of maintaining a DC level of a digital video signal at a fixed level, in which a pedestal level in a vertical blanking period of the digital video signal after an A/D conversion is sampled, and an average value of a plurality of sampling data in a plurality of fields is calculated by an average value calculator. The average value is compared with a predetermined clamp level reference value by a comparison output circuit, and depending on the comparison result, a signal either added or subtracted by a certain width to or from an output signal of a predetermined period before is output for automatically controlling a clamp voltage.