| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide technologies to obtain noise and distortion free characteristics for a D-class amplifier without feedback from a power amplifying part. Ž<P>SOLUTION: The D-class amplifier 10 has a modulation part 20 which is composed of first to N-th modulators 21a to 21n, a modulator selector 30 which selectively switches between the first to the N-th modulators 21a to 21n in the modulation part 20, and the power amplifying part 40 which is a D-class amplifier that amplifies pulse signals output from the modulation part 20. The first to the N-th modulators 21a to 21n have distortion characteristics different from each other, and the modulator selector 30 selects a modulator which has a small distortion (the rate of distortion) corresponding to an input signal amplitude. A switch controller 31 has a hysteresis so that switching is not performed for every period when a frequency higher than the sinusoidal wave of a predetermined frequency is input, and minimizes noise in association with switching. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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