PURPOSE: To decrease the number of elements by constituting the phase comparator circuit with 4 units of the RS flip-flop consisting of the discrete element or the discrete element and the IC element.

CONSTITUTION: In phase comparator circuit 20, reference signal Ref is supplied to the set input ends of RS.FF21, 23 with input signal Sig supplied to the set input ends of FF22, 24 each. Q outputs Q1' and Q2' of FF23, 24 are supplied to the set input ends of FF21, 22 each; and Q' outputs P' and N' of FF21, 22 are supplied to NOR gate 25. Then the output X of NOR gate 25 is supplied to the reset input ends of FF23, 24. At the same time, Q' output P' of FF21 is supplied to the gate of P- channel MOS transistor 27 of charge pump 26. On the other band, Q output N of FF22 is supplied to the gate of N-channel MOS transistor 28 of pump 26 each.