| 摘要 |
PROBLEM TO BE SOLVED: To provide a separately-excited pulse width modulation D class power amplifier having a low cost and a high fidelity. SOLUTION: The separately-excited pulse width modulation D class power amplifier negatively feeds back a feed-back signal Sf to a pulse width modulator 1 (comparator) without passing an amplifier, and inputs an audio signal via a current output amplifier 8 connected to the negative feedback side terminal B of the modulator 1. The amplifier 8 has an extremely high impedance. Thus, since the feedback signal Sf is returned to the modulator 1 without being attenuated, the fidelity of the amplifier is improved. Since the added amplifier 8 does not need to pass a switching pulse signal, the D class amplifier having the high fidelity at a low cost can be constituted of general purpose discrete electronic components.
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