Stereo and dual audio signal identifying circuit

摘要

A stereo and dual audio signal identifying circuit including an FM detector receiving a second intermediate frequency signal, a bandpass filter, an AM detector. The circuit further including an amplifier having a first input receiving an output signal from the AM detector, and a second input receiving a signal derived from a series connected resistor and DC-filtering capacitor connected between the second input and ground, and having a feedback resistor connected between the second amplifier input and the amplifier. The amplifier drives a second stage of the circuit including a voltage controlled oscillator, a phase detector and a low-pass filter. The particular disposition of the DC-filtering capacitor within the circuit allows the capacitor to be externally connected to a single pin in an IC package incorporating the circuit.