In a method of detecting a fault in a class D amplifier, an amplifier output signal is generated based on inverting a pulse width modulation signal corresponding to received audio data. The amplifier output signal is low pass filtered and hysteretically filtered (Schmitt Triggered). The filtered amplifier output signal is sampled (latched) using the pulse width modulation signal as a sampling (latch) clock signal, to generate a first comparison signal. The pulse width modulation signal is sampled (latched) using the filtered amplifier output signal as a sampling (latch) clock signal, to generate a second comparison signal. A fault detection signal for detecting the fault is generated by comparing the first and second comparison signals. Since the first pulse width modulation signal and the filtered amplifier output signal are robustly compared, a fault occurrence may be directly and reliably detected.