AUTOMATIC GAIN CONTROLLING CIRCUIT

PURPOSE:To prevent the production of noise due to rapid fluctuation in an input signal level, by connecting a diode in parallel with a resistor in an integration circuit obtaining a gain controlling voltage from a detected output. CONSTITUTION:A signal received on an antenna 1 is introduced to a high frequency amplifying circuit via a DX/LOCAL changeover switch 7 and an audio signal is obtained at a frequency converting circuit 3, an intermediate frequency amplifying circuit 4 and a detection circuit 5. The output of the detection circuit 5 is introduced to an integration circuit 9 to reject the audio component and the gain of the circuits 1 and 3 is controlled with the DC component. If an input signal to the high frequency amplifying circuit 2 is rapidly changed, since the output of the integration circuit 9 is not rapidly changed, noise is produced from a speaker. To prevent this noise, a diode D is connected in parallel with a resistor R and the capacitor C is rapidly charged with an output exceeding the forward voltage.