A Method to Improve CMRR for CMOS Operational Amplifier by Using Feedforward Technique

Eitake IBARAGI  Akira HYOGO  Keitaro SEKINE  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E80-A   No.2   pp.356-359
Publication Date: 1997/02/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section LETTER (Special Section on Analog Circuit Techniques for System-on-Chip Integration)
Category: 
Keyword: 
analog integrated circuits,  operational amplifier,  common-mode gain,  CMRR,  

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Summary: 
In this paper, two types of improved CMRR CMOS OAs, N type and P type, without common-mode feedback and the cascode current mirrors, are proposed. The CMRR of proposed OAs are enhanced by compensating variations in tail bias current, caused by a common mode input signal, at the differential input stage, by means of feedforward controlled current source. Simulation results show that the CMRR of the proposed OAs are 20dB higher than that of conventional OAs.