Noise eliminating circuit with automatic gain control

Abstract

A noise eliminating circuit for detecting and eliminating a noise pulse component included in an amplitude modulated wave, characterized by a circuit arrangement wherein an output of a detector circuit which is adapted to receive an input signal from an IF stage is coupled to an input of a band-pass filter through a noise amplifier; an output of said band-pass filter is coupled to an input of a pulse generator circuit; an output of said pulse generator circuit is connected to a gate circuit for stopping an audio AGC control operation and a gate circuit for eliminating a noise; an output of said noise amplifier is connected to an AGC control circuit through said gate circuit for stopping the audio AGC operation in order to apply an audio AGC control signal to said noise amplifier; and an output of said band-pass filter is connected to said AGC control circuit in order to apply a noise AGC to said noise amplifier; whereby said pulse generator circuit generates a pulse in response to the detection of the noise signal when the level of the noise signal outputted from the band-pass filter exceeds a given level to trigger said gate circuit for stopping the audio AGC operation and said gate for the noise elimination.