Amplifier unit and method of detecting failure in the same

The present invention provides an amplifier unit including a carrier amplifier biased for Class A or Class AB operation; a peak amplifier biased for Class B or Class C operation, wherein an input signal is input to the carrier amplifier and the peak amplifier, and wherein output signals from the carrier amplifier and the peak amplifier are synthesized to output therefrom; a comparator configured to compare a gate bias voltage of a transistor device in the peak amplifier with a predetermined threshold voltage and output a first output signal; and a failure detection circuit configured to output a second output signal indicating presence or absence of failure, based on the first output signal received from the comparator.