Abstract:A single-chip high-efficiency 3.3V/0.7W class- D audio power amplifier is presented in this paper. Pulsedwidth- modulated technique with bridge tied load is used in this class-D amplifier design. Compared with traditional lowefficiency class-AB amplifiers, this class-D amplifier has the efficiency of 91%. A 4 Ω load is used for amplifier design. The lowest total harmonic distortion is 0.64% when a 250 KHz triangle wave is used. The efficiency will increase when output power is increased. TSMC CMOS 3.3 V/0.35um process is used for this amplifier design.