The development of the High Frequency Power MOSFET has brought about a need for accurate models. Now that the frequency range of these MOSFETs is in domains where typically scattering parameter measurements are used, a broad band device model can prove to be extremely useful. This thesis summarizes the research performed towards the development of a wideband Gate model for the Motorola MRF162 High Frequency Power Transistor. The device theory for typical MOSFETs will be explained. This theory will lead into the development of the Power MOSFET and its associated frequency limitations. The benefits of Time Domain Techniques will be explained and how a wideband model is achieved from this technique. The result from the analysis of the measurements and the device theory is a wideband Gate model developed for the frequency range from 100MHz to 400MHz. Verification is achieved by curve matching the measured Time Domain Reflected waveforms with the simulated waveforms generated using a proprietary program Modified Transient Analysis Program (MTCAP) and by comparison of expected and simulated parasitic values. / Master of Science