DERIVING A THIRD COLOUR-DIFFERENCE SIGNAL FROM OUTPUTS OF TWO PUSH-PULL COLOUR DEMODULATORS

摘要

A first resistive current path is DC connected between respective output terminals of push-pull color demodulator. A second resistive current path is DC connected between respective output terminals of a second push-pull color demodulator. An output color-difference signal is formed by a differential amplifier having one input DC connected to an asymmetrically positioned point in first resistive current path, and a second input DC connected to an asymmetrically positioned point in second resistive current path. Output color-difference signal corresponds to a combination of the demodulated signals, with a polarity relationship and magnitude ratio determined by the asymmetry of positioning of the takeoff points in the respective current paths. Output quiescent voltage is independent of the asymmetry of positioning of the takeoff points.