Amplifier unit and method of detecting failure in the same

The present invention relates to an amplifier unit and a method of detecting failure, in which failure in a peak amplifier of a Doherty type amplifier unit and also failure in the amplifier unit as a whole can be detected with a simplified configuration. A gate bias voltage of a peak amplifier (1-4) is compared with a predetermined voltage in a failure detection circuit (1-6). Based on the resulting voltage, a first signal indicating presence or absence of failure is output. In addition, the failure detection circuit (1-6) receives an output signal from a gain detection circuit (1-5) that detects reduction in the total gain of an amplifier portion including at least a carrier amplifier (1-3). Then, the failure detection circuit (1-6) outputs a second signal indicating presence or absence of failure, based on the first signal, which indicates anomaly in the gate voltage in the peak amplifier (1-4), and the output signal from the amplifier detection circuit (1-5).