Receiver with an AGC circuit capable of expanding a dynamic range

Claim 1

A receiver comprising: a demodulator; an AGC circuit including: a low noise amplifier for amplifying a reception input signal, an AGC amplifier connected to said low noise amplifier for producing an amplified signal which is used as an input signal for said demodulator, and said AGC amplifier having a controlled gain so as to keep an average amplitude of said demodulator input signal at a constant level, and detecting means connected to said low noise amplifier and supplied with an output signal of said low noise amplifier for detecting an input field strength to produce a strength indication signal indicative of said input field strength; a bias control circuit connected to said detecting means, said bias control circuit including means for supplying a bias voltage from a bias voltage source to said low noise amplifier when said strength indication signal from said detecting means has a signal level lower than a predetermined first threshold level, for interrupting supply of said bias voltage when said signal level of said strength indication signal increasingly reaches said first threshold level, and for allowing supply of said bias voltage when said signal level of said strength indication signal is thereafter decreased to a predetermined second threshold level lower than said first threshold level; and a level output circuit connected to said bias control circuit for keeping said strength indication signal at a predetermined high level when supply of said bias voltage is interrupted.