| 摘要 |
PURPOSE:To obtain a horizontal synchronizing circuit having high noise eliminating ability by using a transmission gate realizable by CMOS-IC as a phase comparator. CONSTITUTION:A composite video signal of negative synchronism is impressed to a signal input terminal 51 and synchronizing separated by an amplitude separating transistor TR52, and a positive synchronizing signal is supplied to an input terminal 54 of a transmission gate made up of CMOS-IC through a buffer 53. Further, a comparison signal from a frequency divider is supplied from a comparison input terminal 56 to a control input terminal 55 of a transmission gate. An LPF is connected to an output terminal 57 of the transmission gate. The comparison signal from the frequency divider controls the transmission gate, and takes in the synchronizing signal when the comparison signal is ''H'' level, and does not make phase comparison while the transmisstion gate is off. Thus, the influences of noise included in the synchronizing signal are excluded. |
