JPS642414A - Limiter circuit - Google Patents

Abstract

PURPOSE: To suppress the output of an amplitude component contained in an input signal by simple constitution and to improve an AM removal ratio by connecting a resistance element in series with the input side of a capacity element in a limiter circuit constituted by cascading plural limiter amplifiers through the capacity element.

CONSTITUTION: Resistances R7 and R8 are interposed between the output terminals of 1st and 2nd emitter follower circuits 12 and 13 and capacitors C1 and C2. The output waveforms Va and Vb of those two circuits 12 and 13 are limited and become constant after the point tc of time of the zero crossing of an input signal. The input waveform of the 2nd limiter amplifier 14 is determined by the capacity values of the capacitors C1 and C2, the values of the resistances R7 and R8 connected in series with the capacitors C1 and C2, and an output limiter level Vc. The limiter circuit, therefore, makes its output waveform constant irrelevantly to variation in the amplitude of the input signal only by inserting the resistances. Consequently, the AM removal ratio can be improved by using the limiter circuit in front of an FM demodulating circuit.

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