Panasonic Intellectual Property Management Co., Ltd.

Hirotsugu Kawata

Yuji Mizuguchi

Toshihiko Kurosaki

Seigo Ozaki

An amplifier is capable of reducing the quantization error caused by conversion accuracy in an A/D converter circuit and, particularly, capable of improving the S/N ratio and distortion rate when an input audio signal is small. In an amplifier () using a voltage variable power supply () as a power supply to follow an input audio signal level (S) to the amplifier () in order to increase or decrease the level of supply voltage supplied to a power amplifier stage (), when the level of source power of the power amplifier stage () is changed, the voltage level of a reference voltage supplied to an A/D converter () of a negative feedback circuit is controlled.

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Kanagawa, Japan

Hirotsugu Kawata