Gaas Mesfet Is And Hemt Large-signal Model

GaAs crystal is a kind ofⅢ-V compound semiconductor material with excellent performance. GaAs semiconductor devices and integrated circuits are widely used because of their high speed of information processing, super-high frequency, low power consumption and low noise. GaAs devices and integrated circuits show their importance in microwave communication and military application. MESFETs and HEMTs are the most universal and mature devices in GaAs circuits. With these excellent figures of merits of GaAs, the great attention was paid on GaAs MESFET and HEMT.The large-signal analysis is an attractive topic because it is an important and tough issue. An accurate large-signel model of GaAs MESFET and HEMT is very important for computer-aided design in design of microwave/Radio-Frequency devices and circuits, though modeling of GaAs MESFETs and HEMTs is complicate for the nonlinear characterization when the FETs operate in the condition of large signel. The study on the large-signal characteristic of GaAs MESFETs and HEMTs adopting widely applied equivalent-circuit approach is presented in this paper.First of all , a small-signal model for GaAs MESFETs and HEMTs is established, and a method of extracting series resistance, parasitic inductance, parasitic capacitance and intrinsic element parameters for HEMT small-signal equivalent circuit is described. Then the large-signal-equivalence-circuit model is established based on the small-signal model analysis. The Charlmers model which is one of empirical models is applied in the large-signal analysis. The most important nonlinear elements, such as the Drain current Ids and the Gate capacitance Cgs, Cgd have been modeled in Charlmers model, because they are the key parts of the large-signal equivalent circuit. Measured and modeled dc are compared and found to coincide well. Finally a new parameter model according to the parameters extracted from Charlmers model is described. It can resolve the problem of the discrete of measure`datas. Many large signal models can be obtained through the new parameter model. Good accuracy of the new model is demonstrated through comparing the model and the measure results.The research of this thesis can be a good reference of the MMIC design.