Stability analysis of power amplifiers

The paper presents recent advances on stability-analysis methods, applied to power amplifiers, which often exhibit undesired behavior. Techniques will be provided to detect the most common types of bifurcations, or qualitative changes of the solution stability when a parameter is varied continuously. The bifurcation analysis techniques are combined with pole-zero identification in order to detect an undesired coexistence of stable solutions. Bifurcation loci provide instability contours versus practical design parameters and can be used to evaluate the impact of the instability on the overall amplifier performance and to stabilize the amplifier. Various examples of usual instability phenomena in power amplifiers will be presented.