Improved linearity low area CMOS multifunctional structures

Abstract

In this article, original low-power low-voltage multifunctional structures with improved performances are presented, which allow implementation (with minor changes in the design) of four important functions: signal gain with theoretical null distortions, voltage multiplication with very good linearity and simulation of a perfect linear resistor with both positive and negative equivalent resistance. The great advantages of the increased modularity and controllability and of the associated reduced design costs represent an immediate consequence of the multiple functions realised by the proposed structures. The linearity is strongly increased by implementing the original techniques, while the silicon occupied area per function is reduced as a result of the proposed multifunctionality. The structures are implemented in 0.35 µm CMOS technology and are supplied at ±3 V. The circuits present a very good linearity (in the worst case, total harmonic distortion, THD <0.75% for differential amplifiers and active resistors and THD <0.95% for the multiplier), correlated with an extended range of the input voltage (at least ). The tuning range of the active resistors is approximately hundreds of kiloohms to megaohms.