Radio receiver signal amplifier and AGC circuit

摘要

An integrated circuit is employed to provide a high gain signal amplifier having an automatic gain control function and an output suitable for driving signal detection circuitry in a radio receiver. The circuit operates at the receiver intermediate frequency. A gain controlled cascode amplifier drives one input of a high gain differential amplifier. The other input is returned to a reference potential. A pair of current mirrors are coupled into the differential amplifier to provide a pair of single ended outputs. One output drives a peak rectifying diode to operate the automatic gain control and the other output drives a signal detection circuit. The current mirrors are ratioed so that the automatic gain control threshold is a predetermined fixed multiple of the signal threshold.