Patent ID: 7043033

Claim:
An apparatus, comprising: a first amplifier that is configured to amplify an input signal to provide an output signal; a reference voltage circuit that is configured to selectively provide a reference voltage, wherein the reference voltage is generated by providing a charging current to a capacitor such that the capacitor charges to a desired voltage level; a buffer amplifier that is configured to receive the reference voltage and selectively provide a ground return for the output signal that corresponds to the reference voltage when the buffer amplifier is activated; and a terminal that is coupled to the buffer amplifier such that a voltage associated with the terminal corresponds to the reference voltage when the buffer amplifier is activated; and a mode detection circuit that is arranged to monitor the reference voltage, monitor the voltage associated with the terminal, and determine an operating mode by evaluating the voltage associated with the terminal when the reference voltage reaches a predetermined level, wherein the operating mode corresponds to a AC coupled operating mode when the terminal is coupled to a circuit ground, and the operating mode corresponds to a DC coupled operating mode when the reference voltage exceeds the voltage associated with the terminal.