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A new design methodology for wideband, multi-stage, multi-bit ΣΔ modulators (ΣΔMs) with improved dynamic range, is presented. The key to improving dynamic range is to have the first stage oscillated, then the coarse quantisation noise vanishes and hence circuit non-linearities do not cause a leakage quantisation noise problem. Based on the proposed methodology, a fourth-order four-bit ΣΔM can achieve the dynamic range of 80 dB at the OSR of 8 without using additional calibration techniques.
Date of Publication: 27 May 2004