PURPOSE: To make it possible to use a discriminator for a wide-band FM carrier wave, by inserting a negative feedback circuit, which consists of a resonating circuit having a resonance frequency different from a resonating circuit for amplitude modulation, to a selecting circuit having the resonating circuit for amplitude modulation above to reduce the gain of the selecting circuit.

CONSTITUTION: If resonance frequency f01 of negative feedback circuit 9 in selecting circuit 2 is made different from resonance frequency f02 of resonating circuit 4 and Q of them are set to approximately equal values, the impedance becomes larger according as the characteristic approaches frequency f01, and the series feedback quantity is increased to reduce the gain of circuit 2. Meanwhile, the impedance becomes larger according as the characteristic of circuit 4 approaches frequency f02, and the gain is increased. Since the characteristic of circuit 2 is a characteristic obtained by synthesizing both characteristics above, linearity of the inclination part is improved and the discriminator can be adapted to a wide band simply by selecting frequencies f01 and f02 properly. Consequently, the discriminator which can be used for the wide-band FM carrier wave can be obtained with a simple constitution.