| 摘要 |
A power amplifying apparatus which is of a switching type and capable of efficiently amplifying a power of an input AC signal such as an acoustic signal, includes a first switch circuit ( 11 ) and a second switch circuit ( 12 ) to which a power supply voltage Vc is applied, an inductor ( 13 ) and a load ( 14 ) which are connected between the switch circuits, and a control circuit ( 15 ) which receives an input AC signal Vi, sets a predetermined ratio of ON/OFF periods, and drives the switch circuits. The control circuit ( 15 ) includes an arithmetic circuit ( 20 ) which multiplies a modulation sensitivity (for example, an amplitude of a triangular wave voltage used for generation of a pulse signal for driving a switch circuit) by a ratio (Vc/Ec) of the power supply voltage Vc and a DC component Ec thereof. This configuration can compensate for distortion caused by a ripple variation of the power supply voltage due to regenerated power or the like, and enable a gain control by the power supply voltage.
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