| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique for making compact an output voltage control circuit which controls the output voltage of a power supply circuit supplying an operating voltage to a speaker amplifier, in accordance with the operation state of the speaker amplifier. SOLUTION: The peak holding circuit, included in an output voltage control circuit which performs operation control over the power supply circuit which is supplied with a plus voltage BVDD and a ground voltage VSS, and supplies the potential difference between the plus voltage VPP and minus voltage VMM to each speaker amplifier as the operating voltage, includes first to third N-channel field-effect transistors which are applied at respective drains thereof with the voltage BVDD and applied at respective gates thereof with voltages corresponding to output signals of the respective speaker amplifiers and the ground voltage VSS, and have respective sources connected in common, and outputs a voltage developed at the common connection point of the sources. COPYRIGHT: (C)2011,JPO&INPIT
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