A power supply device for driving first and second amplifiers includes a first power generator, a second power generator, a charge pump and a control unit. The first power generator provides a first voltage for first power reception ends of the first and second amplifiers. The second power generator provides a second voltage. The charge pump is coupled between the second power generator and a second power reception end of the first amplifier and between the second power generator and a second power reception end of the second amplifier, and is used for generating a third voltage for the first and second amplifiers according to the second voltage. The control unit is coupled to the second power generator and is used for controlling the second power generator, so as to adjust the second voltage to make the third voltage equal to a multiple of the first voltage.