Combined Electrical and Thermal Parameter Extraction for Transistor Model

A transistor parameter extraction method is presented where the device heating during the measurement is taken into account. The method utilizes an electrothermal transistor model including thermal feedback, as well as a proper model for the heat diffusion from the active region of the transistor. Here a simple but physically justified model for the thermal spreading impedance of the transistor is applied. It is based on the thermal impedance of a heat generating sphere that is synthesized with a simple electrical equivalent circuit. An example is given where model parameters of a MESFET are extracted by concurrently fitting the thermal and electrical parameters to the measured drain transient currents. Electrothermal simulations and optimizations are performed with the circuit simulation tool APLAC.