A.A. Kapralova, L.V. Manchenko, V.M. Lukashin, A.B. Pashkovskii, V.A. Pchelin
Nonlinear models are the main method of MESFET’s and HEMT’s representations in modern CAD program systems intended for power amplifiers.
Most of typical methods for nonlinear model extraction utilize measured transistor S – parameters. При этом возникает ряд вопросов связанных с точностью вычленения S-параметров именно самого транзистора. In this situation some problems arise which associated with S – parameters extraction accuracy of the transistor itself
The trouble is that the majority of connectors in the power transistors are much wider than 50 – Ohm line that requires quite difficult bonding.
Ideally the probe testing should be carried out on the specific test cell or cells group with gate width much less than gate width of the transistor with consequent scaling.
But for power transistors it is very often too difficult and sometimes (when we simply haven’t special transistor cell) impossible so most of the measuments are carried out in special holder-adapters.
The another two problems emerge
Most of power FET’s have cells structure. But even only one sell is not matching to 50 – Ohm line, it is lead to significant inaccuracy in the measurement of the transistor S – parameters.
Mismatch amplify greatly errors that contact precision adds to the whole S – parameters of the transistor, conduction lines and wires.
In this paper the simple method of contact error reduction for liner model extraction of power FET’s is presented, which have not required further measurements on special cells and scaling.
The technique is based on measuring the same transistor in 50 Ohm lines and then in the specially developed resonant impedance matching network, which connects to the device making minimal parameter perturbation followed by correcting results to allow for theoretical and experimental data agreement.