A Linear CMOS Transconductance Element of an Adaptively Biased Source-Coupled Differential Pair Using a Quadritail Cell

Katsuji KIMURA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E79-A   No.2   pp.184-189
Publication Date: 1996/02/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Analog Technologies in Submicron Era)
adaptive-biasing,  quadritail cell,  OTA,  CMOS,  

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A novel circuit design technique for realizing a linear CMOS transconductance element, consisting of an adaptively biased source-coupled differential pair using a quadritail cell, is proposed. In the circuitry, the quadritail cell, which provides an output current proportional to the square of a differential input voltage, cancels a nonlinear term of the source-coupled differential pair. The circuit have a superior linearity and a wide linear input voltage range compared with the conventional linear CMOS transconductance elements because the transconductance characteristic is theoretically linear over wide input voltage range when all the MOS field-effect transistors (MOSFETs) are operating in the saturation region and the MOSFETs' behaviors are according to the relation based on the square-law characteristic. The proposed adaptively biased source-coupled differential pair was verified by using transistorarrays and discrete components on a breadboard.