PURPOSE: To put a carrier wave in phase in every main scan by counting the carrier wave, and using a counting circuit which is cleared at the rise of a phase signal outputted on every main scan, and forming the carrier wave with the output of the counting circuit.

CONSTITUTION: A reference signal A is inputted to the clock terminal CK of a programmable counter 1 and also inputted to the clock terminal CK of a DFF2. A phase signal B is inputted to the input terminal DI of the DFF2 and the output Q' and a phase signal are ANDed by a gate 3 to obtain a pulse signal C at the rise of the phase signal B. The pulse signal C clears the counter 1. Every time the counter 1 counts the reference signal A by a prescribed number, it outputs a pulse signal D to an FF4. The FF4 inverts the output every time the pulse signal D is applied, and opens and closes an analog switch 5 to perform the amplitude modulation of a picture signal.