TOPAS
Introduction:
This is a sample how an ECAD approach to an electronic-engineering's problem can leads to the solution with precision and accuracy.
When we polarize an active device we want force voltages & currents for the operation that we chose. But we don't know the temperature of junction therefore the calcolus of power dissipation is left to an approximate one, based on thermic-resistance (that we find in the datasheet) and analogy laws. Exist another approach to this problem. Solve a symbolic, exact system based on model of active device, parameters extracted with measurements, and a suitable set of non-linear equation by a numeric cycle and non-linear solving technique (Newton-Raphson Method in our case).
Description:
How you can see,the KVL (Kirckhoff Voltage law), model and parameters converge to the first node and they contribute to the problem formulation. The ICs (Initial Conditions) had been used to inizialize the numerical-NR3x3 cycle (Newton-Raphson 3x3).
After each step, the termination conditions are evalued, and, if the active device not changed the operation functional area (interdition, triode or saturation), the program jump to next step. If this operation area changed a re-formulation of the problem is needed. When the convergence of numerical cycle had reached the program can go on with a data's post-processing from which we can see: the terns Vgs,Vds,Tj (indipendent variables), the error functions, the stories of all stored variable. Also the results are plotted and used for visualization of load's straigth-line in chars-plane and variable's stories.
Results of a cycle for your considerations:
