Common-denominator modelling for stability analysis of electronic circuits

In the local stability analysis of a circuit, the poles of the linearised circuit are investigated. If any of the circuit poles has a positive real part, the found solution for the circuit is unstable. The poles of the linearised circuit are usually obtained by fitting rational models on data samples of the Frequency Response Functions of the linearised circuit. Classically, a single impedance function is modelled to determine the poles. In this paper, it is shown that a common-denominator modelling of multiple impedance functions together can increase the robustness of the rational modelling procedure for stability analysis.