A methodology for the optimal design of modulators in oversampled converters is described. The authors concentrate on two important design constraints, namely power consumption and nonlinearity. The work reflects their research results in the study of modulators, and will be useful to those involved in the design of different types of oversampled converters. The authors have published and communicated some previous results in symposia or conferences. This book is based on Wang’s doctoral dissertation.

The book is structured in six chapters. Chapter 1 reviews the fundamentals of oversampled A/D converters and discusses the principles of multiloop, multistage, and incremental oversampled converters.

Chapter 2 presents various operational amplifier (opamp) topologies used in oversampled modulators. Miller-compensated two-stage opamps, class AB opamps, and dynamic opamps are discussed. The transient behavior of these opamp topologies is analyzed, and a new low-voltage CMOS class AB opamp is proposed.

Chapter 3 includes three issues related to the optimal design of opamps for oversampled converters: the theoretical minimum power bound for an ideal opamp, the best opamp choice in terms of power consumption, and the best strategy to obtain minimum power consumption. The authors develop a model that captures the dynamics of the integrator inside the modulator, and compute the consumption for various topologies. An example demonstrates the strategy for achieving the minimum power for class A opamps.

Chapter 4 presents a new analytical model for opamp-induced nonlinearity in oversampled converters. The model includes both finite slow rate and finite gain bandwidth effects and is valid for both first-order and higher-order modulators. Theoretical predictions are compared with measured results from fabricated integrated circuits (ICs).

Chapter 5 studies other nonlinear phenomena in delta-sigma modulators: nonlinear capacitors, nonlinear reference voltage, and nonlinear DC gain. Ways to minimize the overall nonlinearity are discussed.

Chapter 6 examines the design considerations for building blocks for a first-order delta-sigma modulator. The design tradeoffs to minimize power consumption and nonlinearity are evaluated. Measurements from fabricated ICs are compared to computer simulations in order to demonstrate the principle of the modulator operation.

The authors have found an equilibrium between theory and practice. They present a good mirror of their research methodology. All of the theoretical results are validated by comparison with measures on fabricated products. Simulation is also used to obtain more detailed views of the design products, and the simulation results are also compared with the reality.

The text makes good use of formulas, circuit schematics, diagrams, and graphics. Because the authors treat practical aspects of the subject, the book will be useful not only to researchers, but to engineers and students interested in the design of modulators for oversampled converters. I recommend it as supporting material for university courses on converters.