PURPOSE: To reduce spike noises by providing a switch between a signal output line and a power supply, conducting the switch during the unnecessary signal extracting period to supply directly a power supply voltage to a signal output line.

CONSTITUTION: An MOST111 is controlled by a pulse signal c which is turned on during the horizontal scanning and a horizontal switch 8 is switched sequentially by an output pulse of a horizontal shift register 2. On the other hand, an MOST121 is conducted by a pulse signal D during each horizontal blanking period and each horizontal MOST81 is turned on at the same time at a terminal voltage A to read an excess electric charge. A switch 200 is conducted by a c' signal from an inverter 300, then an output signal line is short-circuited to a video power supply 7. Since the switch 200 has only to be conducted after the period when the horizontal MOSTs are turned on/off simultaneously in this case, the switch 200 is controlled by using the signal D in place of the c' signal.