This text discusses architectures, circuits and procedures for the optimum design of bandpass sigma-delta (SD) A/D interfaces for mixed-signal chips in standard CMOS technologies. The book is detailed and in-depth coverage of switched-current (SI) errors, which supports the design of high performance SI chips. The book starts with a tutorial presentation of the fundamentals of bandpass SD converters, their applications in communications and their most common architectures. It then presents the basic SI building blocks required for their implementation and analyzes in great detail the operation of these blocks. The influence of SI errors on the performance of the SD modulators (SDMs) is also studied. The outcome is a unique set of models which can be employed with a double purpose: namely, to support iterative procedures employed in mapping specifications onto design parameters; and to allow for accurate behavioural time-domain simulation using MATLAB-like tools. The book is completed with two case studies corresponding to modulators for AM digital radio receivers. The analyses, models and procedures in the book support the design of SI front-ends with performance indexes comparable to those of switched-capacitor circuits, which makes a significant difference as compared to previous works in the area of SI circuits. Together with a detailed revision of the SI literature, the book presents practical recipes on how to get the maximum performance from SI circuits, and illustrates them by means of two case study chips in CMOS submicron technologies. These prototypes constitute the first reported IC realizations of SI bandpass SDMs. This text contains valuable information to be used as a reference by designers of the analogue front-end of mixed-signal chips. The models presented in the book will help these designers to increase their productivity. The tutorial, comprehensive coverage of all issues associated with bandpass sigma-delta converters makes the book very well suited for graduate courses.