Good Thesis on CMOS Opamp from Georgia Tech 2004
oliv...@gmail.com
Authors: Sengupta, Susanta
Electrical and Computer Engineering
Abstract: The performance of analog integrated circuits is dependent
on the technology. Digital circuits are scalable in nature, and the
same circuit can be scaled from one technology to another with
improved performance. But, in analog integrated circuits, the circuit
components must be re-designed to maintain the desired performance
across different technologies. Moreover, in the case of digital
circuits, minimum feature-size (short channel length) devices can be
used for better performance, but analog circuits are still being
designed using channel lengths larger than the minimum feature sizes.
The research in this thesis is aimed at understanding the impact of
technology scaling and short channel length devices on the performance
of analog integrated circuits. The operational amplifier (op amp) is
chosen as an example circuit for investigation. The performance of the
conventional op amps are studied across different technologies for
short channel lengths, and techniques to develop technology-
independent op amp architectures have been proposed. In this research,
three op amp architectures have been developed whose performance is
relatively independent of the technology and the channel length. They
are made scalable, and the same op amp circuits are scaled from a 0.25
um CMOS onto a 0.18 um CMOS technology with the same components. They
are designed to achieve large small-signal gain, constant unity gain-
bandwidth frequency and constant phase margin. They are also designed
with short channel length transistors. Current feedback, gm-boosted,
CMOS source followers are also developed, and they are used in the
buffered versions of these op amps.