DEVICES FOR PROCESSING COLOUR SIGNALS

摘要

A video signal including a carrier chrominance signal is converted by an A/D converter which is clocked by a controllable variable frequency oscillator. A phase comparator compares the phases of the A/D converter output and the clock, and a computing circuit provides the absolute value and sign of the output of the comparator during a burst period. A current source and a current sink whose values are controlled by the aboslute value output and which are turned on (off by the sign output) provide the control to the variable frequency oscillator via a low-pass filter.