Time-domain equivalent design of continuous-time ΣΔ modulators

A new design approach operating in the time domain for the design of Continuous-Time (CT) ΣΔ modulators is presented. The method obtains CT modulators that are exactly equivalent to Sampled-Time (SD) counterpart without any constraint on the shape of feedback DACs responses. The procedure is suitable and powerful for transistor-level studies because design can be performed directly using circuit simulators. The effectiveness of the technique permits to account for the non idealities of integrators and DACs. Analytic study and behavioral simulation confirm the method.