FREQUENCY DEVIATION DETECTOR

PURPOSE:To obtain DC output without ripple, by a method wherein a frequency deviation detector generates DC output depending on deviation between input signal frequency and setting frequency, and integrator and sample and hold circuit are provided in the frequency deviation detector. CONSTITUTION:Output signal of control circuit 16 is supplied to switches 22, 23 through J-K.FF34 and AND circuit 36. Output of the switches 22, 23 is supplied to the integrator 38, and input voltage is integrated in positive direction at previously setting integration time constant. When output of the integrator 38 is held, a sample and hold circuit 40 begins sampling and state is held until reset of output of the integrator 38 thereby DC output Eo is outputted during the operation. The integrator 38 and sample and hold circuit 40 are controlled by a control circuit 42. Output of the integrator 38 at working is integrated in negative or positive direction at the same inclination, and if unknown frequency (f) of the input signal is different from previously setting frequency, integration is effected to a value proportional to the difference thereby output Eo contg. no ripple is obtd.