Generalized multi-stage closed loop sigma delta modulator

This paper presents a new high order cascade sigma delta modulator called GMSCL. It uses first and/or second order modulator with unity signal transfer function in each stage and a global feedback to lower the sensitivity to circuit imperfections, to relax the output swing and gain requirements of amplifiers and to avoid digital prefiltering in the quantization error cancellation logic. The zeros of the noise transfer function are optimized to improve the modulator performance. This topology is thus very suitable for wideband low voltage applications. Behavioral simulations demonstrate the high efficiency of the proposed topology comparing to existing cascade topologies.