DEVICE FOR AUTOMATICALLY CONTROLLING BLACK VIDEO CURRENT LEVEL OF VIDEO DISPLAY UNIT

摘要

A system for automatically controlling the bias of a kinescope in a television receiver comprises an input sampling amplifier, and an input clamping network including a clamp capacitor. A reference voltage developed on the clamp capacitor is applied to the input of the sampling amplifier for establishing its initial reference bias condition. The amplifier conducts during sampling intervals for sampling signal amplitude changes referenced to the reference voltage provided via the clamp capacitor. The amplifier is rendered non-conductive at other times, to thereby effectively decouple the discharge path for the clamp capacitor, whereby the clamp capacitor is prevented from discharging significantly during intervals when the AKB signal processor is not engaged in signal clamping and sampling functions.