Multi-stage delta-sigma modulator with a relaxed opamp gain using a back-end digital integrator

摘要

This paper presents a multi-stage noise-shaping (MASH) delta-sigma modulator (DSM) using a back-end digital integrator in the first stage of the MASH DSM. By using the back-end digital integrator in the first stage, not only can the resolution of the first stage be improved, but the opamp dc gain requirement can also be relaxed. A new structure is proposed which avoids the need for quantization noise extraction digital-to-analog converters (DACs) when using the back-end digital integrator. Applying the proposed scheme, 3-level first stage quantizer will effectively operate as a 15 level quantizer, and accordingly the quantization noise leakage can be reduced. Detailed MATLAB simulation results and mathematical analysis are provided to prove the efficiency of the proposed structure.