Low power sigma delta modulator with dynamic biasing for audio applications

In this paper, a low power sigma delta modulator with dynamic biasing technique is presented. According to the analysis of the operations of the switched-capacitor integrator, the folded-cascode operational amplifier can be designed with optimized biasing currents in three different phases to reduce power dissipations. The total power saving is 20% of the general one. A prototyping fourth order single-bit MASH 2-2 sigma delta modulator is designed with the technique of dynamic biasing to achieve dynamic range of 95 dB and peak signal-to-noise-and-distortion-ratio of 93 dB. The experimental circuit is designed in 0.35 mum 2P4M CMOS technology. The chip area is 3.11 mm², and the power dissipation is only 5 mW from a supply voltage of 3 V.