A class-AB linear transconductor with enhanced linearity

Abstract

In this paper a novel linear transconductor topology is proposed, where class-AB behavior based on adaptive biasing is exploited to improve the linear range. The adaptive biasing circuit is based on the Winner-Take-All topology already used for class-AB OTAs, and optimized to improve the linearity, and the proposed transconductor features a gain control input for tunability. The transconductor provides a gain of 43 μS while consuming 70 μW. The linear range (1% variation of the dc transconductance gain) is 470 mVpp, about 4.5 times larger than for the corresponding class-A cell. Total harmonic distortion is improved by about 15 dB, and good results in terms of linearity and noise are reported with respect to the state-of-the-art. Simulations of a Gm-C biquad filter based on the proposed transconductor are also reported to validate the design.