A Rail-To-Rail Op-Amp with Constant Gm Using Current Switches

Author

Xichuan, Wang ; Huan, Deng ; Ting, Zhang

Author_Institution

Microelectron. R&D Center, Shanghai Univ., Shanghai

fYear

2007

fDate

26-28 June 2007

Firstpage

1

Lastpage

3

Abstract

A scheme to achieve constant Gm for rail-to-rail CMOS op-amps is presented. It is based on a novel concept that employs four transistors as current switch to select different differential pairs as input pairs for different common-mode voltage. The operation of the two differential pairs is separated, so they can be regulated for constant Gm for the whole input common-mode voltage range. An OTA stage is used at the output for better frequency response and precisely controlling of output current. There is no requirement for any precise analytic relationship between drain current and transconductance, this is particularly important as it makes the circuit useful for deep submicron CMOS technologies. And it can work for supply power of 2.5V~5.5V. With GSMC 0.18um CMOS process, the simulation results show that the gain can achieve 80 dB. And the CMRR is improved also.

Keywords

CMOS analogue integrated circuits; operational amplifiers; switching circuits; CMOS op-amp; CMRR; GSMC CMOS process; OTA stage; common-mode voltage; current switches; deep submicron CMOS technology; gain 80 dB; rail-to-rail operational amplifier; size 0.18 mum; Breakdown voltage; CMOS technology; Circuit simulation; Frequency; MOSFETs; Operational amplifiers; Power supplies; Rail to rail inputs; Switches; Transconductance;

fLanguage

English

Publisher

ieee

Conference_Titel

High Density packaging and Microsystem Integration, 2007. HDP '07. International Symposium on

Conference_Location

Shanghai

Print_ISBN

1-4244-1252-8

Electronic_ISBN

1-4244-1253-6

Type

conf

DOI

10.1109/HDP.2007.4283626

Filename

4283626