Circuit analysis programs are standard tools in industry for the design of electric circuits. The automatic modelling process for the network creates differential-algebraic equations. They differ considerably from ordinary differential equations in theory and in numerical properties. This is demonstrated at simple circuits. Standard integration routines are based on the backward difference formulas. Their possible shortcomings and restrictions are discussed. An alternate approach based on special taylored one step methods is introduced. The performance in theory and a practical implementation in an industrial software package are presented.

The work was supported by the federal government BMBF.