A Numerical Analysis of the Transient Behavior of a Transistor Circuit

This paper describes some difficulties encountered in the numerical solution of nonlinear circuit equations. A particular transistor circuit is analyzed to illustrate the nature of the difficulties and how they may be resolved. In this circuit it is possible, without sacrificing accuracy of the physical model, to eliminate unimportant stray parameters whose presence destroys the efficiency of most integration routines. A method based on a potential function is used for deriving the circuit equations and it is shown how these equations can be systematically reduced upon removing the stray parameters. Application of such techniques to the circuit considered reduced the calculation time (on an IBM 7094) from 30 minutes to 7 seconds.