A rigorous yet simple method for determining stability of linear N-port networks [and MMIC application]

The authors describe a technique for easily calculating normalized determinant function using return ratios. It is shown that an elegant yet simple relationship exists between the return ratios of each dependent source in a linear network and Platzker´s normalized determinant function. Using this relationship, the stability (or instability) of linear N-port networks containing any number of active devices can easily be determined using commercially available circuit simulators. An example is shown where this new technique correctly predicts instability in a GaAs MMIC power amplifier.<>