Color television signal demodulation system

TLDR: In this article, a monolithic integrated circuit consisting of three sets of full-wave, synchronous, switched demodulators is used to demodulate the red, blue and green color signals present in a composite television signal.

Abstract: A silicon monolithic integrated circuit consisting of three sets of full-wave, synchronous, switched demodulators is used to demodulate the red, blue and green color signals present in a composite television signal. Each of the demodulators consists of two pairs of switching transistors with the transistors in each of the pairs being rendered alternately conductive by a reference signal derived from the reference oscillator in a color television receiver. The phase of the red and the blue reference oscillator signals are obtained in a conventional manner, and the phase for the green reference signal is obtained by adding a predetermined portion of the red and blue signals together in a resistive adder to provide the green oscillator signal. The color signals are supplied in alternate phase to the two pairs of switching transistors in each of the demodulators, and the brightness signal components are applied equally or push-push to the switching transistors of the demodulators through an input transistor for each of the demodulators. In order to provide the proper relative amounts of gain for three demodulators, the red and blue signal demodulators have shunting resistance circuits connected across the input transistor circuits; and the green demodulator has a shunt connected across equal taps on voltage dividers connected to the outputs thereof. Since the brightness signal components are balanced with respect the the shut devices, the brightness signal passes through all of the demodulators unaffected by the shunting circuits.