Phase discriminator circuit

Abstract

An integrating phase discriminator circuit has an integration circuit including an operational amplifier to integrate bidirectional rectangular waveforms originating from those portions of two AC inputs having the same polarity. When an integrated value reaches an operating detecting level V.sub.D11 of a level detector when said level is equal to an integrated value V.sub.H for a phase difference of 90.degree. between the two inputs, an inoperative signal from the level detector changes to an operating signal. This causes an R-C differentiation circuit to apply a position pulse to the operational amplifier to forcibly raise the integrated value of its upper limit E.sub.P while a control circuit changes V.sub.D11 to a reset detecting level V.sub.D22 =E.sub.P -V.sub.H in the level detector, resulting in the continuous delivery of the operating signal. When the integrated value decreases to V.sub.D22, the level detector delivers the inoperative signal. The differentiation circuit then generates a negative pulse for forcibly lowering the integrated value to its lower limit of 0 through an operational amplifier. The level detector continuously delivers the inoperative signal while it has the detecting level changed from V.sub.D22 to V.sub.D11 by the control circuit.