Amplitude detecting method, AGC circuit gain controlling method, amplitude detecting apparatus and AGC amplifier circuit

摘要

In an amplitude detecting circuit, a phase shifter, into which an alternating current signal that is outputted from an AGC circuit is inputted, outputs first and second alternating current signals between which there is a phase difference. In addition, full wave rectifying is carried out in a first full wave rectifier on the first alternating current signal that is outputted from the phase shifter and in the same manner full wave rectifying is carried out in a second full wave rectifier on the second alternating current signal. Furthermore, in an averaging circuit, output signals of the first and second full wave rectifiers are averaged so as to generate an amplitude detection signal.