Novel Low-Voltage Linear OTAs Employing Hyperbolic Function Circuits

Fujihiko MATSUMOTO  Yasuaki NOGUCHI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E83-A   No.6   pp.956-964
Publication Date: 2000/06/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section of Papers Selected from 1999 International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC'99))
analog integrated circuits,  OTAs,  low-voltage analog circuits,  linear circuits,  

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In this paper, new linearization techniques for low-voltage bipolar OTAs using hyperbolic function circuits are described. First, a design of an exponential-law circuit, which is a basic building block to compose hyperbolic sine and hyperbolic cosine circuits, is proposed. This circuit is simpler than the conventional circuit and is suitable for low-voltage application. Next, two linearized OTAs using the hyperbolic function circuits are presented. The transconductance is given by maximally flat approximation. Although designs of the OTAs are different, the output currents are given by the same expression. Finally, performance of the OTAs is discussed. The linear input voltage range of the proposed OTAs is almost the same as that of the conventional OTA. However, one of the proposed OTA has no more than two-thirds the power dissipation of the conventional one. The other has a superior high-frequency characteristic.