| 摘要 |
PROBLEM TO BE SOLVED: To suppress a variation in voltage of a battery and an influence in noise in an on-vehicle power amplifier. SOLUTION: The power amplifier device is provided with a DC line filter 23 to which the output voltage of a battery 21 loaded on a vehicle is supplied and a non-feedback power amplifier 10 which is operated with the output voltage of the DC line filter 23 as a power supply voltage +VDD. The unit is equipped with a level control circuit 12 for controlling the level of an audio signal to be supplied to the power amplifier 10 and a voltage comparator circuit 32 for comparing the level of the output voltage of the DC line filter 23 with a reference value DREF. The compared output of the voltage comparator circuit 32 is supplied to the level control circuit 12 as its control signal to cancel a variation in level of the output signal of the power amplifier 10 caused by a variation in output voltage of the battery 21. COPYRIGHT: (C)2003,JPO
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