A novel low-power low-voltage Class D amplifier with feedback for improving THD, power efficiency and gain linearity

Class D amplifiers (amps) are conventionally designed as feedforward circuits primarily due to the difficulty of feeding back the digital pulse width modulated output. We analytically investigate the design of Class D amps with feedback and propose a feedback circuit design. We show that the performance of low-power (mWs) low-voltage (1.1-1.4 V) Class D amps embodying our feedback design is significantly improved. The improvements include substantially reduced distortion, improved power efficiency (reduced DC output static bias current), improved gain linearity and lower cost (not requiring post-fabrication trimming), and are achieved with simple hardware. We verify our circuit design proposal by computer simulations and on the basis of measurements on prototype ICs.