Meeting and Seminar Archive:
Date: Sep 21, 2009 [Co-sponsored with IEEE SCV CAS]
Title: Low-Voltage Oversampling Analog-to-Digital Conversion
Speaker: Dr. Bruce A. Wooley (Robert L. and Audrey S. Hancock Professor of Engineering, Dept. of E.E.) Stanford University
Abstract: Through the exchange of resolution in time for that in amplitude, oversampling methods are now widely used to enable the realization of high-resolution analog-to-digital converters in scaled CMOS VLSI technologies. So-called oversampling modulators combine coarse quantization at sampling rates well above the Nyquist rate with feedback and subsequent digital signal processing to avoid the need for precision analog circuits. Such modulators were originally conceived in the mid-twentieth century in the form of delta modulators, which digitize the rate of change of a signal, rather than the signal itself. However, noise-shaping modulators that directly encode the signal proved to be a more robust approach and have subsequently come into widespread use. In particular, cascades of inherently stable sigma-delta (or, equivalently, delta-sigma) modulators are an efficient means of extending the dynamic range of oversampling converters that are largely immune to both analog circuit imperfections and fundamental stability concerns. This presentation begins with an overview both architectural and circuit issues associated with the design of noise-shaping modulators, and then presents examples of some approaches to their implementation under increasingly severe constraints on power dissipation and supply voltage.
Bruce A. Wooley is the Robert L. and Audrey S. Hancock Professor of Engineering at Stanford University. He received the B.S., M.S. and Ph.D. degrees in Electrical Engineering from the University of California, Berkeley in 1966, 1968 and 1970, respectively. From 1970 to 1984 he was a member of the research staff at Bell Laboratories in Holmdel, NJ, and he joined the faculty at Stanford in 1984. At Stanford he has served as the Chair of the Department of Electrical Engineering, the Senior Associate Dean of Engineering and the Director of the Integrated Circuits Laboratory. His research is in the field of integrated circuit design, where his interests include low-power mixed-signal circuit design, oversampling A/D and D/A conversion, circuit design techniques for video and image data acquisition, high-speed embedded memory, noise in mixed-signal integrated circuits, and circuits for wireless and wireline communications.
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