This text discusses architectural and circuit considerations for optimizing the design of oversampled A/D interfaces for mixed-signal CMOS ASICs. The mathematical background is presented and it is suitable for novices in the field. Practical recipes on how to get the maximum performance from these kinds of circuits are presented and illustrated through three converter prototypes in CMOS submicron technologies. A feature of this book is the presentation of a systematic methodology for increasing the productivity of engineers in the design of high-performance modulators. It uses optimization at the architecture and the circuit levels, together with hierarchical transmission of the specifications among levels. The tasks of architecture selection, architecture sizing and building block sizing are supported by CAD tools, thus allowing designers to obtain demanding modulator specifications in short design cycles. The book is organized such that it can be used for a graduate course on S modulator design. In addition, the book is a reference for designers who want to improve their productivity in the design of oversampled mixed-signal interfaces.