Introduction to ΣΔ Modulators: Fundamentals, Basic Architecture and Performance Metrics

This chapter presents an introduction to ΣΔ converters. It analyses the benefits of employing oversampling and quantization noise shaping in the digitization of signals and compares with the Nyquist‐rate analog‐to‐digital converters (ADCs). The chapter focuses on the ΣΔ modulator, including its general architecture, ideal operation, and performance metrics. It also analyses the simplest topology of a ΣΔM ‐ based on a first‐order loop filter ‐ to illustrate the principles of operation behind ΣΔ techniques that achieve high accuracy with low‐resolution embedded quantization. The chapter discusses the limitations of first‐order ΣΔMs ‐ caused by the strong correlation between the quantization error and the input signal. It highlights the methods for increasing the effective resolution of ΣΔMs. The chapter explores how to build both ADCs and digital‐to‐analog converters (DACs) using ΣΔMs. In both, the core building block is the ΣΔM, which is implemented in the analog domain in ADCs and in the digital domain in DACs.