Patent ID: 6242981
Filing Date: 2001-06-05
Classification: H03G

Abstract:
An automatic gain control (AGC) circuit comprising:a variable gain amplifier supplied with an input signal for controlling a gain thereof and outputting an output signal;a detecting circuit for detecting the output signal from the variable gain amplifier and outputting a voltage having a level changed in correspondence with a level of the output signal from the variable gain amplifier; anda voltage to current converting circuit for converting the voltage output from the detecting circuit into a current,wherein the voltage to current converting circuit includes a differential amplifier to which the voltage output from the detecting circuit is supplied,wherein a current output from the differential amplifier is supplied to a capacitor to thereby convert the current into an AGC voltage,wherein AGC is carried out by controlling the gain of the variable gain amplifier by the AGC voltage, andwherein a time constant of the AGC circuit is changed by changing an alternating current amplification factor of the differential amplifier by changing a magnitude of an operating current of the differential amplifier.