A class D amplifier capable of compressing a dynamic range and reproduction by changing on a real time basis a modulation ratio to a non-linear ratio in accordance with amplitude of an input signal. The class D amplifier including a triangular waveform generation circuit that generates a deformed triangular waveform used as a comparison waveform for amplitude modulating an analog input signal, the triangular waveform generation circuit comprising a pulse generation circuit for generating a plurality of first pulse signals, a plurality of pulse extraction circuit for extracting said first pulse signals selectively, and for outputting second pulse signals during the time according to extracted first pulse signals, a plurality of three state buffers to which a clock pulse signal for basic cycles is provided as an input signal, one of said second pulse signals is provided as a control signal, and said clock pulse signal for basic cycles is output during a period for said one of second pulse signal is provided, and a integration circuit, having a time constant thereof changing in accordance with the output of said three state buffer, for generating said deformed triangular waveform corresponding to the time constant based on the clock pulse signal for basic cycles.