Patent ID: 8416968

Claim:
An audio device, coupled to an audio port, comprising: a capacitor, coupled to the audio port; a load, coupled to the audio port; an output amplifying circuit, operated at a first working voltage, for outputting a first audio signal to the audio port, wherein the first working voltage has a first positive voltage and a first negative voltage such that a direct current (DC) level of the first audio signal is substantially zero volts; and an input amplifying circuit, operated at a second working voltage, for receiving a second audio signal from the audio port, wherein when the audio port is in an output state, the output amplifying circuit is enabled and the input amplifying circuit is disabled, and when the audio port is in an input state, the input amplifying circuit is enabled and the output amplifying circuit is disabled, wherein an output of the output amplifying circuit is coupled to a first end of the capacitor and an input of the input amplifying circuit is coupled to a second end of the capacitor.