Rigorous, HB-based nonlinear stability analysis of multi-device power amplifier

This paper presents a rigorous numerical approach to the stability analysis of multi-device power amplifiers. As well known, amplifiers exploiting symmetrical power dividing and combining networks exhibit both even-mode and odd-mode instabilities, the latter being impossible to detect in a input-output port small-signal stability assessment. In the present paper, a global non-linear stability analysis is exploited to analyze such cases, with the aim of detecting possible differences between small-signal and large-signal stability conditions, and to drive the design therefrom. The present technique is also indispensable whenever the stability of intrinsically nonlinear amplifier stages (such as class B or class F amplifiers) is investigated without resorting to conservative, worst-case approaches (such as relying on class-A stability assessment).