Extending the Stable Input Range of a Single-Bit Sigma-Delta Modulator with a Saturation Element

Abstract

This paper presents a simple compensation scheme for extending the stable input range of a single-bit sigma-delta (Σ-Δ) modulator that is normally stabilized in sliding mode. The proposed control scheme requires a saturation element that provides additional feedback to modify and stabilize the modulator loop filter when the modulator is going to lose stability due to large input level. The proposed compensation scheme is easy to implement and is only activated when the input level is exceedingly large, so it does not affect the performance of the modulator with its input in the normal range. A third-order sigma-delta modulator with an extended input range was designed and implemented to demonstrate the practicality of the proposed design. 