Closed Loop Class-D Amplifier with Nonlinear Loop Integrators

In many integrated class-D audio amplifiers large linear capacitors are used to create the triangular reference signals for generation of PWM signals. In this paper, an integrated class-D amplifier is presented that uses a control loop with area efficient nonlinear gate oxide capacitors. A model is used to show that the nonlinearity does not degrade the THD performance. A comparison with a similar control loop using linear capacitors is made. Measurements and simulations on two amplifiers with linear and nonlinear capacitors confirm that nonlinear capacitors do not introduce additional distortion.