Recent Advances on the Design of High-Gain Wideband Operational Transconductance AmplifiersReport as inadecuate

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VLSI DesignVolume 2009 2009, Article ID 323595, 11 pages

Review ArticleDepartment of Electrical Engineering, Analog and Mixed Signal Center, Texas AandM University, College Station, TX 77843, USA

Received 4 March 2009; Accepted 18 May 2009

Academic Editor: Chang-Ho Lee

Copyright © 2009 Rida Assaad and Jose Silva-Martinez. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Feed-forward techniques are explored for the design of high-frequency OperationalTransconductance Amplifiers OTAs. For single-stage amplifiers, a recycling folded-cascode OTA presents twicethe GBW 197.2 MHz versus 106.3 MHz and more than twice the slew rate 231.1 V-𝜇s versus 99.3 V-𝜇s as a conventional folded cascode OTA for the same load, power consumption, and transistor dimensions. It is demonstrated that the efficiency of the recycling folded-cascode is equivalent to that of a telescopic OTA. As for multistage amplifiers, a No-Capacitor Feed-Forward NCFF compensation scheme which uses a high-frequency pole-zero doublet to obtaingreater than 90 dB DC gain, GBW of 325 MHz and better than 70∘ phase margin is discussed. The settling-time- of the NCFF topology can be faster than that of OTAs with Miller compensation. Experimental results for the recycling folded-cascode OTA fabricated in TSMC 0.18 𝜇m CMOS, and results of the NCFF demonstrate the efficiency and feasibility of the feed-forward schemes.

Author: Rida Assaad and Jose Silva-Martinez



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