PURPOSE: To eliminate the noise occurring at the switching time of the TV picture receiver or at the channel switching time, by installing the switch between the collector and the emitter of a pair of transistors each which form a differential amplifier.

CONSTITUTION: In case the voltage applied to muting signal input terminal 58 to which the muting signal is applied is high enough to give conduction to transistors 7 and 8 as well as to give no conduction to transistors 5 and 6 each, the AM demodulation signal does not flow at all to load resistance 15. And only the DC current flows to resistance 15, and the current value becomes to L0/2. This means the state under which the muting is applied, and no demodulation signal emerges at demodulation signal output terminal 54. In addition, the DC voltage of terminal 54 becomes exactly equal to the case in which no muting is applied, i.e., in case terminal 58 is in a low level. Accordingly, the noise caused by the break of the muting can be eliminated.