Bias dependence of the MODFET intrinsic model elements values at microwave frequencies

S-parameters of MODFETs were measured versus bias instead of frequency with a special feature of the HP8510 network analyzer. Figure of merit plots, f_T, and f_max, were quickly generated from the bias sweeps of S-parameters, and optimum bias points were easily found. The intrinsic device elements of MODFETs were calculated after de-embedding the measurements from the device parasitics. The technique is demonstrated with a 0.15-μm pseudomorphic MODFET with an f_T of 150 GHz. The usefulness of the technique for understanding the operation of the MODFETs is discussed. With this technique a bias scan of an intrinsic element value can be measured and plotted in 13 s