PURPOSE: To realize a frequency discriminating circuit on an integrated circuit(IC) with no external parts and in a circuit constitution quite different from a pulse count type wave detecting circuit by using such component parts that can be easily transformed into an IC as a switched capacitor amplifier, a DC voltage generator, a clock generator, etc.

CONSTITUTION: The clocks 1 and 2 inputted from a clock generator 2 using a frequency modulation signal VIN as its input are inputted to a switched capacitor amplifier 1 together with the fixed voltage VREF inputted from a DC voltage generator 2. Then the output V'OUT of the amplifier 1 is outputted as an output signal VOUT via a smoothing filter 4. Each block forms such a circuit constitution that can be easily transformed into an IC without using any external element. Thus a frequency discriminating circuit is formed on an IC with no use of a special external element.