A Quasi-Analytical Method for Extraction Small-Signal Model Parameters of Microwave Power Transistors with High Electron Mobility Based on Gallium Nitride Technology

In the recent decade, GaN HEMT power transistors have gained increasing popularity among radar power amplifier designers. To design a microwave power amplifier using a GaN HEMT transistor, we need a large-signal model for the transistor, which accurately characterizes its behaviour. The first step to implement large-signal modelling is to build small signal modelling. The small-signal model of a transistor can be apportioned into two extrinsic and intrinsic parts. For the extraction of intrinsic elements, the extrinsic elements should be extracted at first. In this paper, The Parasitic capacitors and inductors of a typical transistor are calculated directly and without the need for optimization at low frequencies using measurement results in different operating conditions. And then with a few matrix conversions and direct relationships, the parasitic resistors of the transistor at a bias point belong to the active region (no need for gate-source voltage greater than zero) are calculated. The improved method is verified by comparing the simulated small-signal S-parameter with the measured data up to 10GHz. Results indicate that the error is less than 4% in the operating frequency band of the transistor. In comparison with counterpart optimization methods, this method takes less time and is less complicated.