music, guitars & other obsessions

Symbolic Equations & Circuit Analysis

I am gradually putting together a “simplified” methodology for analyzing electrical circuits by symbolic means – I don’t believe the subject was taught in many engineering schools today, and certainly not when I was in school (or perhaps just not at my school). There are a number of areas that require one’s attention:

1) the theory – the articles and textbooks by Dr. Middlebrook (Caltech) and Dr. Vorperian (was Middlebrrok’s student at Caltech);

2) analytical tools – SAPWIN or its successor QsapecNG (from University of Florence, Italy);

3) symbolic math software – Mathcad.

Why go through all this regiment when the Spice programs could easily do the job? The motivation is two fold: 1) take a peek “behind the scene”, since the Spice programs pretty much hide away all the mathematical derivations from the user, so that even someone without any idea of how a circuit functions could still do simulations (as many bad examples on the net have shown); and 2) to better understand how the circuit works and to highlight the key components within the design. It is hoped that with better understanding, improved designs could be made in the future and/or to modify and improve an existing design.

Another minor point on the math software, I kept going back to Mathcad even though there are more robust software like Matlab, Mathamatica, Octave, etc. The main reason is that I prefer the interface, it is direct – and it is NOT a programming language (which is also its weakness), it’s pretty much WYSIWYG, write the equations, plug in the values, write your comments just as you would writing a paper – it is a linear process, I guess better suited for my simple-minded way of thinking.


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