Receiver with an AGC circuit capable of expanding a dynamic range

摘要

A receiver comprises an AGC circuit including a low noise amplifier for amplifying a reception input signal and an AGC amplifier, a level detection circuit for producing a strength indication signal indicative of an input field strength, and a demodulator. The receiver has a function of controlling a gain to keep an amplitude of a demodulator input signal at a constant level. A bias control circuit controls on and off of a bias voltage source to allow and inhibit supply of a bias voltage to the low noise amplifier when the strength indication signal has a signal level lower than and not lower than a first threshold level, respectively. When the signal level is thereafter decreased to a second threshold level lower than the first threshold level, the bias control circuit turns on the bias voltage source to supply the bias voltage. A level output circuit serves to keep the strength indication signal at a predetermined high level when the bias voltage source is turned off.