Polynomial Feedback of Noise Shaping Filter for Fully Digital Audio Amplifier

This paper proposes a noise shaping filter with polynomial nonlinear feedback for the fully digital audio amplifiers. The fully digital audio amplifier has several merits and has become used in commercial products, but the use of the uniform PWM brings additional harmonic distortion and floor noise. The nonlinear feedback eliminates the distortion caused by the uniform PWM and are realized in polynomial form. By expressing the nonlinearities in polynomial form, the storage for the nonlinear table can be reduced and the dead time compensation for the class-D amplifier becomes possible.