| 摘要 |
PURPOSE:To attain composite peak value type and keyed type gain control operation with a comparator whose reference value is fixed by making a gain of an amplifier amplifying a luminance signal based on the synchronizing tip variable depending on the burst period and a period not. CONSTITUTION:A differential amplifier circuit 13 whose amplifier gain is switched by a burst gate pulse between a luminance/chrominance separating circuit 4 and an inverting input terminal of a comparator circuit 12. The differential amplifier circuit 13 is provided with a resistor circuit 15 including a awitch 14 closed during the burst gate period and the amplifier gain is made different depending on the burst gate period and any other periods by means of the switch 14. As a result, since the comparison input to the comparator 12 is different depending on the keyed type and the peak value type gain control operation, the peak value type and keyed type gain control operation are made composite by the comparator whose reference value is fixed. |
