The AM-FM detector circuit is of integrated circuit format and comprises as an input stage, a differentially connected emitter follower pair (24, 26) which functions: in FM-mode to pass the more dominant one of two incoming FM-IF signals which are phase-displaced on a continuously variable basis about a 90 phase displacement at the FM-IF carrier frequency, and in AM-mode to operate as a full wave rectifier on two incoming, 180 phase displaced, AM signals. Onward of the input stage there is an FM-channel which includes a zero-crossing detector (33), and an AM-channel which includes a linear differential amplifier (37), and finally an ouput amplifier (41) which delivers, in either FM or AM mode, the recovered audio, and either an FM-AFC or AM-AGC signal. The detector circuit incorporates significant improvements, designed to insure temperature stability, compensation for variations in the IC fabricating process, over-all stability and especially dc-stability, and to provide, in AM-mode improved AGC performance and minimized audio distortion.