A power supply device for driving an amplifier includes a power generator for providing a first voltage for a first power reception end of the amplifier, a power conversion unit coupled to the power generator, for converting the first voltage into a second voltage, a charge pump coupled between the power conversion unit and a second power reception end of the amplifier, for generating a third voltage for the amplifier according to the second voltage, and a control unit coupled to the power conversion unit, for controlling the power conversion unit, so as to adjust the second voltage to make the third voltage equal to a specific multiple of the first voltage.