One embodiment of an apparatus for testing an amplifier includes an amplifier having a driver and a filter, the filter being connected between an output of the driver and an output of the amplifier. The filter is operable to produce a demodulated output signal from a higher frequency modulated signal at the driver output. The apparatus also includes a voltage level detector connected to the driver output and a control circuit operable to detect at least one fault based on a voltage level measured at the driver output by the voltage level detector.