An amplifier device includes a regulator circuit, a first voltage converting circuit, a first control circuit, and an amplifier circuit. The regulator circuit is configured to output a first driving voltage. The first voltage converting circuit is coupled to the regulator circuit, and is configured to output one of the first driving voltage and at least one first voltages related to the first driving voltage, as a first operating voltage. The first control circuit is coupled to the first voltage converting circuit through a first node, and is configured to receive the first operating voltage and generate a first operating signal according to the first operating voltage and a first control signal. The amplifier circuit is coupled to the first control circuit and the regulator circuit, and is configured to receive the first driving voltage, and is controlled by the first operating signal to generate an output voltage.