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 two integrators, analog switches corresponding to the integrators, 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 integrated by a pair of integrators 38, 40, and output of the integrators 38, 40 are applied through corresponding analog switches 42, 44 to a sample and hold circuit 48 thereby DC output E0 is formed. The integrators 38, 40 and analog switches 42, 44 are controlled by a control circuit 46. Output of the integrators 38, 40 at working is integrated in negative or positive direction at the same inclination, and if unknown frequency (f) of input signal is different from previously setting frequency, integration is effected to a value proportional to the difference and sample and hold action is effected. Thereby output E0 with polarity and amount depending on the deviation and without ripple is obtained.