Published in Proceedings of the 39th IEEE Midwest Symposium on Circuits and Systems: Ames, IA, Volume 2, August 18, 1996, pages 957-960.
Copyright © 1996IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. The definitive version is available at http://dx.doi.org/10.1109/MWSCAS.1996.588120.
NOTE: At the time of publication, the author Vladimir Prodanov was not yet affiliated with Cal Poly.
A CMOS op-amp input and gain stage suitable for low voltage operation are introduced. The input stage operates in strong inversion and has common-mode range beyond rail-to-rail. It uses two complementary differential pairs connected in parallel. The common-mode dependent current biasing employs only four transistors, does not require additional voltage references, current switches and/or current mirrors and does not increase the minimum required supply voltage. The variation of the net transconductance is approximately 15% over the entire common-mode range. The gain-stage has constant output resistance. In addition it reduces the variation of the net transconductance due to variations in μn/μp ratio.
Electrical and Computer Engineering