The LM1863 is a high performance AM radio system intended primarily for electronically tuned radios Important to this application is an on-chip stop detector circuit which allows for a user adjustable signal level threshold and center frequency stop window The IC uses a low phase noise levelcontrolled local oscillator Low phase noise is important for AM stereo which detects phase noise as noise in the L-R channel A buffered output for the local oscillator allows the IC to directly drive a phase locked loop synthesizer The IC uses a RF AGC detector to gain reduce an external RF stage thereby preventing overload by strong signals An improved noise floor and lower THD are achieved through gain reduction of the IF stage Fast AGC settling time which is important for accurate stop detection and excellent THD performance are achieved with the use of a two pole AGC system Low tweet radiation