An audio amplifier includes a timing control circuit, an amplifying circuit, and a bias control circuit. The timing control circuit generates a first power down signal and a second power down signal, in which the first power down signal is asserted before the second power down signal is asserted. The amplifying circuit receives a bias voltage to amplify an audio signal and is deactivated when the first power down signal is asserted. The bias control circuit provides the bias voltage for the amplifying circuit and is deactivated when the second power down signal is asserted.