FM demodulator integrated on semiconductor chip without discrete circuit components

An FM demodulator connected to a de-emphasis filter supplied with a power current and carrying out a de-emphasis for generating an audio-frequency signal, comprising:

• a multiplier for multiplying an audio intermediate frequency signal by an oscillating signal for producing a first output signal representative of a product of the multiplication;
• a low-pass filter connected to said multiplier, and eliminating high-frequency components from said first output signal for producing a demodulated audio-frequency signal;
• a voltage controlled oscillator connected to said low-pass filter, and responsive to said demodulated audio-frequency signal for controlling a frequency of said oscillating signal, said voltage controlled oscillator having a first resistor and a first capacitor both fabricated on a semiconductor chip and forming parts of a time constant circuit of an astable multivibrator for determining a fundamental frequency of said oscillating signal;
• and
• a temperature compensating amplifier connected to said low-pass filter, and amplifying said demodulated audio-frequency signal for generating a second output signal supplied to said de-emphasis filter, said temperature compensating amplifier generating a first reference current passing through a second resistor fabricated on said semiconductor chip and a second reference current passing through a third resistor implemented by a discrete component outside of said semiconductor chip so as to suppress a variation of an amplitude of said demodulated audio-frequency signal due to temperature dependency characteristics of said time constant circuit.