| 摘要 |
In an audio amplifier having a D-class power amplifier, a noise upon muting is suppressed. There are provided a sampling rate converter circuit 23 for sampling rate converting a digital audio signal S 11 into a digital audio signal S 23 , and a DeltaSigma modulation circuit 14 for re-quantizing the digital audio signal S 23 into a bit-reduced digital audio signal S 14 . Further, there are provided a PWM modulation circuit 15 for converting the digital audio signal S 14 into a PWM signal S 15 , and a D-class power amplifier 16 to which the PWM signal S 15 is supplied. Still further, there are provided a dither signal forming circuit 18 for superimposing a dither signal SDI on the digital audio signal S 23 , and a forming circuit 19 for forming a muting signal SDET. Upon muting, an input side of the sampling rate converter circuit 23 is stopped by the muting signal SDET.
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