Dual-gate FET modelling

The dual-gate FET (DGFET) is a four terminal device which is usually operated in a common source configuration. The first gate, next to the source, is used as the input port and the drain as the output port. The presence of the second gate, which is used as a control terminal, gives the DGFET its great versatility as verified by the wide variety of microwave circuit applications that have been demonstrated. These have included automatic gain control amplifiers, frequency multipliers, mixers, phase shifters, switches and power dividers. Despite its versatility the DGFET is not commonly used in microwave circuits due to a poor understanding of its operation and a lack of accurate and efficient modelling techniques. Since the device operation is nonlinear a model that is capable of accurately and efficiently predicting large signal performance of DGFET circuits is required. The device can be represented by either physical or equivalent circuit models but both have their merits and disadvantages. The suitability of both modelling techniques for the large signal modelling of DGFETs is investigated