PURPOSE: To simplify circuit constitution by controlling the operation of a transistor for the second power supply, which supplies negative voltage to load, making use of the output voltage of a transistor for the first power supply, which supplies positive voltage to load.

CONSTITUTION: The operation of a transistor 16 for a second power supply, which is so provided as to supply negative voltage to second load 14, is controlled by making use of the output voltage of a transistor 15 for the first power supply, which is so provided as to supply positive load to first load 13. That is, by controlling the operation of either transistor 15 (16), the power supply operation to the load 13 (14) is controlled. Hereby, the circuit constitution can be simplified.