Design and Characterization of Wide-Tuning CMOS Active Inductors for RF and Microwave Applications

This chapter presents the design, implementation, and evaluation of a tunable active inductor implemented in standard 130 nm CMOS technology. Two topologies are proposed: a single-ended implementation based on an enhanced cascode-grounded gyrator-C structure, and a differential topology incorporating negative-resistance compensation. In this design, independent inductance/quality factor (Q) tuning is achieved in the single-ended circuit through a dual control mechanism represented by the feedback resistor and bias currents, while the differential topology expands this concept to take advantage of cross-coupled devices for loss cancellation, offering enhanced Q and wide inductance tunability. The two structures were fabricated and measured, and both post-layout simulated and measured results exhibit compact silicon area, wide frequency tunability, excellent Q-factor performance, and low noise figures. The proposed tunable active inductors feature great robustness to PVT variations and are ideally suitable for integration into RF building blocks including filters, oscillators, and low-noise amplifiers.