To reduce the distortions of the output signal of a digital amplifier by eliminating the distortions of triangular wave signal.

An integrating part INT of a triangular wave signal generator TRI is provided with a fully differential amplifier AAMP, and a rectangular wave signal Vrec1 supplied form a rectangular wave generation circuit OSC and a rectangular wave signal Vrec2 supplied from an inverter INV are respectively integrated and generate triangular wave signals Vtri1, Vtri2. A differential amplifying part DIF amplifies the voltage difference of the two triangular wave signals Vtri1, Vtri2 supplied from the integrating part INT, and the triangular wave signals Vtri1, Vtri2 become opposite in phase; and even if a distortion voltage is superimposed on the triangular wave signals Vtri1, Vtri2, distortion voltage is canceled, due to the nonlinearity of the integrating part INT and the effects of noise signal.