Adaptation in Standard Cmos Processes with Floating Gate Structures and Techniques

Title of dissertation: ADAPTATION IN STANDARD CMOS PROCESSES WITH FLOATING GATE STRUCTURES AND TECHNIQUES Yanyi Liu Wong Doctor of Philosophy, 2007 Dissertation directed by: Professor Pamela Abshire Department of Electrical and Computer Engineering We apply adaptation into ordinary circuits and systems to achieve high performance, high quality results. Mismatch in manufactured VLSI devices has been the main limiting factor in quality for many analog and mixed-signal designs. Traditional compensation methods are generally costly. A few examples include enlarging the device size, averaging signals, and trimming with laser. By applying floating gate adaptation to standard CMOS circuits, we demonstrate here that we are able to: • Trim CMOS comparator offset to a precision of 0.7mV. • Reduce CMOS image sensor fixed-pattern noise power by a factor of 100. • Achieve 5.8 effective number of bits (ENOB) in a 6-bit flash analog-to-digital converter (ADC) operating at 750MHz. The adaptive circuits generally exhibit special features in addition to an improved performance. These special features are generally beyond the capabilities of traditional CMOS design approaches and they open exciting opportunities in novel circuit designs. Specifically, the adaptive comparator has the ability to store an accurate arbitrary offset, the image sensor can be set up to memorize previously captured scenes like a human retina, and the ADC can be configured to adapt to the incoming analog signal distribution and perform an efficient signal conversion that minimizes distortion and maximizes output entropy. The thesis is organized as follows: chapter 1 outlines a general overview for the scope of this research; chapter 2 provides a background for discussion, chapters 3 to 5 describe in detail the implementation of the floating gate adaptation, prototype design, and experimental result for the comparator, the ADC, and the imager, respectively; finally, chapter 6 summarizes the work. ADAPTATION IN STANDARD CMOS PROCESSES WITH FLOATING GATE STRUCTURES AND TECHNIQUES