The title of this book could easily have been called Variations on a Theme by Middlebrook, or Applications of The Extra Element Theorem and its Extensions. Neither title, however, would have captured the unique message of this book that one can solve very complicated linear circuits in symbolic form almost by inspection and obtain more than one meaningful analytical answer for any transfer function or impedance. The well-known and universally practiced method of nodal or loop analysis not only becomes intractable when applied to a complicated linear circuit in symbolic form, but also yields unintelligible answers consisting of a massive collection of symbols. In a meaningful analytical answer, the symbols must be grouped together in low-entropy form – a term coined by R. D. Middlebrook – clearly indicating series and parallel combination of circuit elements, and sums and products of time constants. The illustrative examples in Chapter 1 serve as a quick and informal introduction to the basic concepts behind the radically different approach to network analysis presented in this book.

Today, the only method of circuit analysis known to most engineers, students and professors is the method of nodal or loop analysis. Although this method is an excellent general tool for obtaining numerical solutions, it is almost useless for obtaining analytical solutions in all but the simplest cases. Anyone who has attempted inverting a matrix with symbolic entries – sometimes as low as second-order – knows how tedious the algebra can get and how ridiculous the resulting high-entropy expressions can look.