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

Phanumas KHUMSAT  Apisak WORAPISHET  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.12   pp.2293-2296
Publication Date: 2007/12/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.12.2293
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Electronic Circuits
Keyword: 
operational transconductance amplifier,  OTA,  active-RC filters,  MOSFET-C filters,  feedforward,  

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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 NMOS pseudo-differential amplifier with PMOS active load. The output stage relies upon the dual-mode feed-forward class-AB technique (based on an inverter-type transconductor) with common-mode rejection capability that incurs no penalty on transconductance/bias-current efficiency. Simulation results of a 0.5-V 100-kHz 5th-order Chebyshev filter based on the proposed OTA in a 0.18 µm CMOS process indicate SNR and SFDR of 68 dB and 63 dB (at 50 kHz+55 kHz) respectively. The filter consumes total power consumption of 60 µW.