A Topology of Fully Differential Class-AB Symmetrical OTA With Improved CMRR

An improvement of a standard fully differential class-AB symmetrical operational transconductance amplifier (OTA) topology is proposed in this brief to enhance the common-mode behavior. Common-mode behavior could be critical in fully differential class-AB OTAs, where the total current is not fixed a...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. II, Express briefs Express briefs, 2018-11, Vol.65 (11), p.1504-1508
Main Authors: Centurelli, Francesco, Monsurro, Pietro, Parisi, Gaetano, Tommasino, Pasquale, Trifiletti, Alessandro
Format: Article
Language:English
Subjects:
Class-AB
CMOS
common-mode
fully differential
Gain
Logic gates
operational amplifier
Operational amplifiers
Power consumption
Power demand
Semiconductor device modeling
Topology
Transconductance
Transistors
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Summary:An improvement of a standard fully differential class-AB symmetrical operational transconductance amplifier (OTA) topology is proposed in this brief to enhance the common-mode behavior. Common-mode behavior could be critical in fully differential class-AB OTAs, where the total current is not fixed and differential to common-mode conversion could therefore be present. A signal proportional to the input common-mode component is generated through a simple low-current auxiliary amplifier and used to modulate a bias voltage, achieving cancellation of the output common-mode component. Simulations in 40-nm CMOS technology show a net improvement of common-mode rejection ratio without affecting differential-mode behavior; the increase in area and power consumption is minimal, with a tradeoff between power and settling time. Simulations of a sample-and-hold exploiting the proposed OTA are presented.
ISSN:1549-7747
1558-3791
DOI:10.1109/TCSII.2017.2742240