An amplifier (1) adapted to receive an input signal and to generate an output signal at an amplifier output (7) according to the input signal, the amplifier (1) comprising: a feedback circuit arranged to provide a feedback signal indicative of the output signal; an error signal generating circuit (12, 44) arranged to receive the feedback signal and generate a digital error signal according to the feedback signal; and an output signal generating circuit arranged to generate the output signal and to receive the digital error signal and to adjust the output signal according to the digital error signal; the amplifier (1) further comprising: a fault detection circuit (50) arranged to receive the digital error signal and to determine the presence or absence of a fault condition at the amplifier output (7) according to the digital error signal and to provide a signal (54) indicative of the presence or absence of the fault condition.