CMOS Inductor Performance Estimation using Z- and S-parameters

A comparison is made between model parameter calculation equations of RF CMOS inductors. Model parameters can be extracted from different equations using as variables either Y-, Z-parameters depending on the circuit configuration of the inductor or S-parameters. Results are based on on-wafer RF S-parameter measurements of a fabricated inductor. Differences appear between results obtained with calculation equations based on Z- and S-parameters, extracted for a differentially driven inductor. Therefore, care must be taken by the designers when evaluating an integrated inductor performance to comprehend the technological and operating environment of the device and to choose the corresponding formulas accordingly.