A topological approach for determining the uniqueness of the DC solution

This paper presents a method focussed on assessing the uniqueness of the DC operating point of transistor networks. It determines the necessary conditions for such a network in order to possess multiple DC operating points. The method is based on purely topological conditions of the network graph, and it is developed by performing graph manipulations in a methodological way with the aim of recognising flip-flop-like structures embedded in the original network. The method is applied to networks containing BJTs, independent current and voltage sources, and positive linear resistors; but it can be easily modified to cope with other kinds of active devices