| 摘要 |
PROBLEM TO BE SOLVED: To acquire an output without unnaturalness in a listening sense even when receiving a signal with a relatively high peak level. SOLUTION: The digital amplifier is provided with; a level detector 41 that detects a level of an input analog signal; a timing circuit 42 that delays the input analog signal whose level is detected by the level detector and provides the delayed analog signal to a variable amplification factor amplifier; the variable amplification factor amplifier 43 that adjusts an amplitude of a reference wave of a triangle shape on the basis of an output of the timing circuit; a comparator 6 that compares the input analog signal with an output of the variable amplification factor amplifier to provide an output of a pulse width modulation wave; and a filter circuit 9 that smoothes an output of the comparator. The timing circuit 42 is provided with a time constant circuit that adjusts a delay amount, and the time constant of the time constant circuit is selected smaller when the level of the input analog signal increases and selected larger when the level of the input analog signal decreases.
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