Stereo and dual audio signal identifying circuit

A stereo and dual audio signal identifying circuit, comprising:

• an FM detector receiving an input signal and generating an FM detected output;
• a bandpass filter receiving the FM detected output and generating a bandpassed output;
• an AM detector receiving the bandpassed output and generating and AM detected output;
• an amplifier generating an amplified signal at an output and comprising;
• a first input receiving the AM detected output,
• a second input connected to ground through a series connected resistor and capacitor, and
• a feedback resistor connected between the output and the second input;
• and,
• a phase-locked loop circuit receiving the amplified signal.

A stereo and dual audio signal identifying circuit, comprising:

• an FM detector receiving an input signal and generating an FM detected output;
• a bandpass filter receiving the FM detected output and generating a bandpassed output;
• an AM detector receiving the bandpassed output and generating and AM detected output;
• an amplifier generating an amplified signal at an output and comprising;
• a first transistor receiving the AM detected output at a first base, and having a first emitter connected to a first constant current source, and
• a second transistor controlling gain of the amplifier and having a second emitter connected to the first constant current source and second base connected to the output through a feedback circuit;
• and,
• a phase-locked loop circuit receiving the amplified signal.