Robust NTF design for continuous time Sigma-Delta modulators

In this paper, a novel empirical-analytical study is performed on the design of low power and robust continuous time Sigma-Delta modulators. The proposed method makes the modulators more stable against the excess loop delay of the feedback loop. Besides, it enforces easy constraints on op-amps of the modulator so that we can realize the op-amps with a unity gain bandwidth identical to the sampling frequency of the modulator. In order to design a more stable Noise Transfer Function (NTF), this method employs both the phase margin (PM) and gain margin (GM) stability criteria.