Practical Considerations In The Use of CMOS Active Inductors

Abstract

The lack of high quality factor integrated inductors is one of the most significant impediments to realizing high performance radio frequency integrated circuits (RFICs) within conventional digital CMOS. As an alternative to lossy passive spiral inductors, several active inductor topologies have been reported elsewhere which promise higher quality factors and small size. Using transistor level simulation, this paper considers two fundamental active inductor topologies with particular focus on their robustness with regard to variation with process, voltage and temperature. Simulation results reveal that these active inductors suffer significant variation in both realized inductance value and quality factor particularly as a function of transistor variability. The effects of this variability in active inductor performance are highlighted through simulation of their use in a lumped element Wilkinson power divider realized with active inductors.