Compact Two-Stage Class-AB CMOS OTA for Low-Voltage Filtering Applications

Phanumas KHUMSAT  Apisak WORAPISHET  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.2   pp.543-546
Publication Date: 2007/02/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.2.543
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Electronic Circuits
Keyword: 
operational transconductance amplifier,  OTA,  active-RC filters,  MOSFET-C filters,  

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Summary: 
A compact OTA suitable for low-voltage active-RC and MOSFET-C filters is presented. The input stage of the OTA utilises the resistive tail-biased differential amplifier and the output stage relies upon the feed-forward class AB technique with common-mode rejection capability that incurs no penalty on transconductance/bias-current efficiency. Analysis on the achievable peak voltage swing of the OTA when employed in filters is given. Simulation results of a 0.5-V 100-kHz elliptic 5th-order filter based on the OTA's in a 2-V 0.18 µm CMOS process indicate the differential peak voltage as large as 0.42 Vp (84% of the supply voltage) at 1% THD with the SFDR of 60 dB and the total power consumption of 50 µW.