A 3rd order 1.5-bit continuous-time (CT) Sigma-Delta (ΣΔ) modulator optimized for Class D audio power amplifier

This paper presents a 3
^rd
order 1.5-bit ΣΔ modulator with distributed feedback and local resonator feedback for a Class D audio amplifier. In order to improve the signal-to-noise-and-distortion ratio (SNDR), without increasing the oversampling ratio (OSR) or the order of the modulator, the modulator uses transmission zeros and 1.5-bit quantization. High level simulations of the modulator show that it has a maximum SNDR value of 82.4 dB and a dynamic range (DR) of 76 dB, for a signal bandwidth of 18 kHz and a sampling frequency of 1.2 MHz. The use of a full-bridge output stage allows 1.5-bit quantization.