A new fourth-order single-loop delta-sigma modulator for audio applications

In this paper, a fourth-order single-loop delta-sigma modulator with a new loop topology is presented. The loop-filter is composed of both feedback and feedforward paths. No active summing element is required in the modulator implementation. The modulator has low integrator output swings and high input dynamic range, resulting in relaxed op amp requirements even for low voltage operation. Simulation results indicate that, 94.5 dB peak S/(N+D) is achievable at a clock rate of 2.56 MHz for a 20 kHz baseband. A prototype of the modulator has been fabricated in a 1.2 /spl mu/m CMOS process and it is currently under test.