PURPOSE: To reduce current consumption and power consumption by serially connecting PIN diode driving parts.

CONSTITUTION: When switches 101A, 104A are turned on, a PIN diode 105A is turned on. When switches 102A, 103A are turned on, a PIN diode 106A is turned on. Since an ON side PIN diode can be selected in accordance with the combination of switches to be turned on, a signal switching circuit or the like can be constituted. Then current consumption and power consumption are calculated. When the voltage drop of a semiconductor switch e.g. is supposed to be O.5V, the sum of voltage drops in the PIN diode driving parts becomes 0.5V+0.6V+0.5V=1.6V and two circuits and about 5 circuits can be respectively serially connected when power supply voltage 5V and 12V.