Improving convergence of algorithms for solving systems of circuit algebraic-differential equations

Nowadays, the majority of circuit simulation programs contain advanced methods for suppressing divergence of algorithms for solving algebraic-differential equations. However, some classes of circuits still cause problems - the circuits with strong feedback, flip-flop circuits, the ones characterized by macro models with unusual elements, and large distributed oscillators. In the paper, a novel method is introduced for improving the convergence with four criteria that are being compared. Unlike similar algorithms focused on an operating point analysis, the method also works in a transient analysis. All the four criteria are thoroughly tested on eight problematic circuits - six of them often diverge in the operating point analysis, and two of them sometimes diverge during the transient analysis.