CONTROL METHOD OF PEAK DIFFERENTIAL WAVE DETECTION TYPE FM DEMODULATING CIRCUIT

摘要

PURPOSE:To suppress the occurrence of an abnormal sound and to perform the complete muting, by applying an AC signal for control to a control input terminal to which the mute pulse is supplied and gives the control to a resonance circuit so that the AC signal level becomes minimum at an output terminal. CONSTITUTION:A peak differential wave detecting circuit 3 contains a resonance circuit 4 provided between input terminals 6 and 7 of a differential amplifier con sisting of transistors 8-11 plus a constant current source 12. A double balance gain control circuit 5 consists of the 1st differential amplifier comprising transistors 16 and 17 and the 2nd differential amplifier connected to a constant current source 20. An Ac signal is applied to a control input terminal 21 in order to avoid (an abnormal sound) that is caused with application of the mute pulse. Then the circuit 4 is controlled so that the amplitude level is set minimum for the AC signal emerging to an aural output.