| 摘要 |
PURPOSE:To eliminate ghost easily, by making the AGC operation ineffective or increasing the time constant of the AGC operation at a part within a vertical blanking period, in receiving a television signal. CONSTITUTION:The time constant of a loop filter 41 of an AGC circuit 6 depends on a resistor 42 and a capacitor 43 mainly, and an AGC voltage is extracted at an output terminal 44. A series circuit comprising a capacitor 45 and a discharging resistor 46 is inserted between the output terminal 44 of the loop filter 41 and ground, and the connecting point of the both is connected to a collector of an NPN transistor(TR)47. The emitter of the TR47 is grounded, and the said switching signal Ps is applied to a terminal 48 led from the base. Thus, when the TR47 turns on while the Ps is a high level, the capacitor 45 is connected in parallel with the capacitor 43 and the time constant is increased accordingly. |
