| 摘要 |
PURPOSE: To reduce the power consumption and to decrease heat generation by switching a power supply voltage at a high speed. CONSTITUTION: The amplifier circuit is provided with a voltage switching means 30 with respect to a power supply voltage fed to a low frequency power amplifier 18. High speed power switching elements Qc, Qd are used for high voltage power supply control for the voltage switching means 30 and it is provided with a voltage comparator means which supplies selectively a high voltage power supply or a low voltage power supply to a low frequency power amplifier 18 through the voltage comparison between the low voltage power supply and an output voltage of the power amplifier 18. They high voltage power supply VPH is fed to the power amplifier 18 before the output voltage of the power amplifier 18 gets higher than a power supply voltage VPL being a low voltage. Thus, the effect of reduction in the power consumption and reduction in heat generation is attained. |
