Coupling circuit combining video and gating signals - reduces input-output cross-talk due to parasitic capacitance

摘要

The coupling circuit combines a video signal (S1) (containing line sync. pulses) and a gating signal (S2) (comprising line sync. pulses and gating pulses between the sync. pulses and in the line blanking period). Zero volts in the video signal is the black level. The gating signal controls two electronic switches (4,13). The first switch gates the video signal through to a first transistor's (32) emitter. The second switch gates a grounded resistor through to the base of a second transistor (23). The collector outputs of the two transistors are combined to give the wanted output signal (S3). The second transistor is a phase inverter. The first transistor is coupled at its base to a biasing voltage divider.