Phase shift circuit and FM detector circuit

An FM detector circuit including;

• a phase shifter comprising a delay apparatus for delaying an input signal by a predetermined time;
• and
• a multiplier for multiplying said input signal and an output of said phase shifter;
• wherein said phase shifter comprises:
• a first switch for accepting a first input signal and for turning on and off;
• a first capacitor that is charged by constant current from a constant current source and discharged by the first switch;
• a first comparator for comparing charging voltage of the first capacitor with reference voltage and obtaining an output having rise timing shifted by a predetermined time from the first input signal;
• a second switch for accepting a second input signal differing in phase from the first input signal by 180° and turning on and off;
• a second capacitor that is charged by constant current from the constant current source and discharged by the second switch;
• a second comparator for comparing charging voltage of the second capacitor with reference voltage;
• and
• signal processing circuit for obtaining, on the basis of outputs of the first and second comparators, signals having phase shifted by a predetermined time with respect to the first and second input signals.