AUTOMATIC GAIN CONTROL DEVICE OF AMPLIFICATION OF VIDEO INTERMEDIATE FREQUENCY

摘要

PURPOSE:To eliminate the ghost exactly by gating a horizontal fly-back pulse at a 1/2 horizontal period before the leading edge of a vertical synchronizing signal not to operate AGC then in a television receiver to which a ghost eliminating device is added. CONSTITUTION:A horizontal fly-back pulse (r) is applied to a pulse gating circuit 12 through a coupling capacitor 11 and is gated by a pulse having an output waveform Y. A gated pulse X becomes a keyer pulse of an IF AGC detector and amplifier 8. Consequently, since the keyer pulse does not exist in the leading edge part of the vertical synchronizing signal in the first field, AGC is not operated for reduction of ghost even if ghost is superposed. AGC is operated after the delay of one horizontal period to reduce the amplitude.