Variable Inductance Planar Spiral Inductors and CMOS Wideband Amplifiers with Inductive Peaking

In this paper, a complete set of variable inductance (VI) planar spiral inductors with MOSFET switch were characterized and modeled for the first time. These VI inductors can be used to optimize the performances of the CMOS wideband low-noise amplifiers (LNAs) with inductive peaking, and to implement low-phase noise voltage-controlled oscillators (VCOs), etc.. Moreover, the experimental results show that the series inductive peaking can effectively improve the bandwidth of the CMOS wideband LNAs. For a CMOS wideband LNA with a 0.58 nH peaking inductor, a 74.2% (from 3.1 GHz to 5.4 GHz) increase in bandwidth were achieved. The measured noise figures (NF) are 2.2 dB at 1 GHz and 4.0 dB at 6 GHz. The measured input third-order intercepting point (IIP3) is -3 dBm at 3 GHz. These results show that the performances of the CMOS wideband LNAs can be improved by inductive peaking, which can be optimized by our developed VI inductors.