Design and implementation of oversampled analog-to-digital converters

ignal processing systems can be divided into data acquisition and data processing components. Whereas modern MOS VLSI technology greatly simplifies implementation of the processing functions by digital means, the same is not true for the data acquisition component, where analog signals have to be conditioned and converted to digital codes. A large number of transistors with small size and high speed is needed for the first task; however, conventional means of implementing analog-to-digital conversion call for a variety of high precision components. As a result, A/D converters are typically implemented using special integrated circuit processes and built on separate chips. This approach is inefficient in two ways, in that it does not take full advantage of VLSI technology and it complicates system implementation by asking for different processes and multiple chip sets. Oversampled A/D converters offer a means of resolving this dilemma. In such converters, sampling at well above the Nyquist rate is combined with negative feedback and digital filtering to efficiently exchange resolution in time for that in amplitude. These converters thus exploit the enhanced density and speed of scaled digital circuits to ease the difficulty of integrating complex analog circuit functions within the constraints of VLSI technology.;In this research, the problem of designing oversampled A/D converters has been addressed. Tools for analyzing and comparing different architectures have been developed. A simulator created specifically for this purpose has been optimized for analyzing linear and nonlinear circuits in the mixed analog and digital environment that is characteristic of oversampled A/D converters. An algorithm has been devised that efficiently estimates the performance of A/D converters and is applicable both to simulation and measurements on actual circuits. The feasibility of these design techniques has been tested with a high-resolution oversampled A/D converter fabricated in a 3...