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

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 V_p (84% of the supply voltage) at 1% THD with the SFDR of 60 dB and the total power consumption of 50 µW.