Compensation of Finite GBW in CT Bandpass SDMs based on Single-OpAmp Resonators with Positive-Feedback

Abstract

In this paper an analysis of the influence of finite GBW in positive-feedback single-OpAmp resonator based CT BPSDMs is presented. The resonators of BPSDMs are often realized by LC tanks, requiring large area for the inductor. Positive-feedback single-OpAmp resonators are trying to solve this drawback, as no inductor is required. However, a large GBW of the OpAmp is necessary to achieve a sufficiently large quality factor. In this work, a system-level model accounting for finite GBW and DC gain for this type of resonator is presented. It allows the full compensation of finite GBW by a newly introduced system-level parameter. By implementing this model in a design environment for BPSDMs, a straightforward and automated design process in the CT domain can be carried out including loopfilter synthesis and STF engineering.