Controlled behaviour of STF in CT ΣΔ modulators

Abstract

One of the most interesting properties of continuous time ΣΔ modulators is their implicit anti-aliasing filter. Unfortunately, peaking in their signal transfer function (STF) demands a ‘no-overload’ filter to precede the modulator. A technique and two new topologies, which can achieve an almost flat STF, are proposed. Meanwhile, the topologies still have the desired feature that the internal nodes contain few input related signals.