Finite GBW in single OpAmp CT ΣΔ modulators

This paper presents a comparison study on single-OpAmp resonators applied in ΣΔ modulators under the influence of nonidealities. In the recent state-of-the-art, single amplifier resonators have been proposed for the loopfilter to reduce hardware and thus power and area. The question arises if the effort for this single amplifier approach is indeed lower compared to the two amplifier approach, or if the single OpAmp has to fulfill much higher requirements, which would make the approach counterproductive. To answer this question, we compare the traditional dual amplifier approach, namely the CRFF and CRFB topology, to two single amplifier approaches for the resonator under the influence of amplifier nonidealities and mismatch. It is shown that the single amplifier resonator can come with significant drawbacks, but when compensated for carefully, can still be advantageously applied.