I. Introduction
RF power amplifier is the last component of transmitter chain before transmission of signal to antenna. Currently, Gallium Nitride (GaN) is considered the most promising device technology for high power amplifier design owing to the exciting material properties of GaN. The advanced traits of GaN such as wide bandgap (3.4 eV), high breakdown voltage, high electron mobility (1500 cm2 V-1 s-1) and high frequency operation (device geometry in micrometer), and ability to form heterojunctions (High Electron Mobility Transistor) make it an ideal candidate for designing of high-power amplifiers (HPAs) [1] – [2]. However, GaN device is still not widely used in the design of HPAs due to unavailability of generic large signal model. An accurate small signal model is the primary requirement in building an overall model, before realization in CAD tool for the analysis and simulation of high frequency circuits and systems.