| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital gain control device, having a simpler configuration than those of prior art and capable of carrying out gain control with little quality deterioration, to provide an audio signal power amplifier employing the same, and to provide a method for them. SOLUTION: This digital gain controller is provided with a delta-sigma modulator 103, wherein a subtractor 108 subtracts any output signal from digital filters 111, 112, 113 from a digital signal received from a over-sampling circuit 102, a re-quantizer 109 applies re-quantization to a digital signal, as a result of the subtraction and provides an output of the result, a subtractor 110 subtracts digital signal as a result of the subtraction from the re-quantized digital signal; and the result is outputted to the subtractor 108 via the digital filters 111, 112, 113. As the attenuation coefficient of a sound volume control signal is increased, the quantization step width of the re-quantizer 109 is increased higher, the order of the digital filters 111, 112, 113 is increased higher, and switches SW1, SW2 are switchingly controlled so as to select one of the digital filters 111, 112, 113. COPYRIGHT: (C)2006,JPO&NCIPI
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