Alternative topologies for sigma-delta modulators-a comparativestudy

摘要

This paper investigates four frequently used modulator topologies,nnamely two single-stage and two multistage architectures. Simplenparametric expressions are derived which describe minimum amplifier gainnand bandwidth requirements for all implementations as well as C-rationmatching conditions for the two multistage circuits. The cumulativeneffect of all amplifier nonidealities, including slewing, is revealed byna discrete-time simulator. This study not only presents accuratenquantitative results that illustrate the negative impact of the mostnstringent amplifier nonidealities but also provides the necessaryninsight to circumvent or minimize these parasitic effects whichnultimately limit performance