Patent ID: 7119802

Claim:
A driving voltage controller for controlling a driving voltage to drive a load by using an alternating current comprising: a High output operational amplifier for outputting a High driving voltage and a Low output operational amplifier for outputting a Low driving voltage, wherein said High output operational amplifier and said Low output operational amplifier each includes a differential input stage and an output stage; an output switch for selecting one of the High driving voltage and the Low driving voltage as the driving voltage to electrically connect the load with either said High output operational amplifier or said Low output operational amplifier in accordance with a predetermined timing; a timing controller for controlling said output switch in accordance with the predetermined timing; and a bias current controller for controlling said High output operational amplifier and said Low output operational amplifier such that a bias current flowing in a differential input stage of an output operational amplifier out of said High output operational amplifier and said Low output operational amplifier in case that the output operational amplifier is not electrically connected to the load via said output switch is reduced less than the bias current flowing in the differential input stage of the output operational amplifier in case that the output operational amplifier is electrically connected to the load via said output switch or only the bias current flowing in the differential input stage of the output operational amplifier in case that the output operational amplifier is not electrically connected to the load via said output switch is interrupted by turning off a transistor included in the differential input stage of the output operational amplifier.