A low power low voltage class D amp based on sigma-delta and bang-bang control

In this paper, we propose two low voltage (1V) power-critical analog class D amplifiers: one based on 3_rd-order sigma-delta modulation and the other on bang-bang control modulation. For circuit simplicity and low power dissipation, we propose to employ our self-tuning inverter--comparators for the integrator-cum-comparator and Schmitt trigger designs. Through the self-tuning mechanism, the inherent threshold voltage of the inverter-comparators is made independent of process and temperature variations. On the basis of simulations, our designs dissipate very low quiescent current ∼20μA @ 1V and feature high power efficiency of > 90% and low THD+N of < 0.1%. Both designs are suitable for power-critical low-voltage biomedical applications including hearing aids.