Transistors (12a, 12b) turn on and off with mutually opposite phase input signals. Capacitors (16a, 16b) discharge when the transistors (12a, 12b) turn on, and capacitors (16a, 16b) are charged by constant current from constant current sources (18a, 18b) when the transistors (12a, 12b) turn off. As a result, a gradually rising voltage is obtained at the positive input ends of comparators (14a, 14b) while the input signals are L. By comparing this with fixed voltages of reference sources (20a, 20b), signals having rise timing shifted from input signals by 90° are obtained. The outputs of the comparators (14a, 14b) are mutually shifted by 180°, and at the rise of these outputs, an RS flip-flop (22) is set and reset so that signals delayed in phase by 90° with respect to the input signals are obtained at its outputs.