Determining the HBT base-collector elements directly from S-parameter data

This paper gives suitable analytic equations for direct extraction of the heterojunction bipolar transistor (HBT) series base resistance R/sub bi/ and base-collector capacitances (C/sub bci/ and C/sub bcx/), elements which determine the transistor maximum oscillation frequency f/sub max/. New expressions, one for R/sub bi/, and the other relating R/sub bi/ and C/sub bcx/ in terms of measured parameters have been developed. On this basis, direct extraction of the inner C/sub bci/ and outer C/sub bcx/ base-collector capacitances is possible, independently and robustly. All expressions are valid at each measured frequency, a useful feature in the control of extraction quality.