chapter  7

Qualitative Analysis

WithMartin Hasler

The main goal of circuit analysis is to determine the solution of the circuit, that is, the voltages and the currents in the circuit, usually as functions of time. The advent of powerful computers and circuit analysis software has greatly simplified this task. The numerical analysis should be complemented by a qualitative analysis, one that concentrates on general properties of the circuit, properties that do not depend on the particular set of circuit parameters. Physical circuits can never be modeled in a satisfactory way by resistive circuits, but resistive circuits appear in many contexts as auxiliary constructs. The most important problem that leads to a resistive circuit is the determination of the equilibrium points, or, as is current use in electronics, the DC-operating points, of a dynamic circuit. The list of basic resistive circuit elements given so far is redundant, and the nullator-norator pairs render the controlled sources superfluous.