Introduction to ΣΔ Modulators: Basic Concepts and Fundamentals
This chapter is conceived as an introduction to analog-to-digital converters (ADCs). Their operation principle consists in combining oversampling, quantization error processing, and negative feedback for improving the effective resolution of a coarse quantizer. These basic concepts are presented in Section 1.1 and their effects on the performance of converters are compared with Nyquist-rate converters. Section 1.2 shows the basic architecture, ideal behavior, and performance metrics of converters, and sketches the architectural alternatives to enhance their resolution.
Before presenting practical topologies for the implementation of modulation, the large variety of the existing realizations is briefly classified in Section 1.3 according to the type of modulator architecture (single loops or cascades), the circuit techniques employed (discrete time (DT) or continuous time (CT)), and the nature of the signals being ...