AM receiver

Claim 1

In an AM receiver having an amplifier stage for amplifying received signals which vary from an extremely low level through a range of usable sensitivity to a high level, said amplifier stage including an automatic gain control means for providing gain variable between a maximum gain level and a minimum gain level, detector and filtering means coupled to said amplifier stage for providing an audio signal, and control means having an input coupled to said detector and filtering means and providing a control signal to said automatic gain control means for changing said gain thereof to a predetermined gain level intermediate said maximum and minimum gain levels when said received signals are at said extremely low level, to said maximum gain level when said received signals are within said range of usable sensitivity, and to said minimum gain level when said received signals are at said high level; said automatic gain control means comprising: first and second bias voltage sources; first and second input terminals receiving said control signal and said received signal, respectively; control current means electrically connected to said first input terminal and responsive to said control signal for producing a control current varying with said control signal; signal current means electrically connected to said control current means and to said first bias voltage source for producing a signal current which varies inversely with said control current; means electrically connected to said control current means, said signal current means, said second bias voltage source and said second input terminal, and modulating said signal current with said received signal to produce an output signal; and output terminal means electrically connected to said signal current means and receiving said output signal through the latter.