How to know the stability of high power amplifier?

hello all
i have Input and output impedance for high power transistor. (zin =real +img)
how can i know if it is stabillity at this point.

best regards
eladg

HF-amplifier?

Possibly not, you need more information as S21 and S12 (gain and loss in each direction) above your know S11 and S21 (Zin, Zout) and in wide range of frequency... (ie matching network impedances on both sides is very importent for stability if transistor have low loss (isolation) between output and input).

Instability point and reactive load (ex. filters outside pass band) can starting oscillating long away from your designed frequency...

read book on RF-PA or microwave design, more or less part of text in book
talk about stability... One, but not best book is 'Microwave transistors amplifiers, analys and design' and can find her in edaboard

One of my concern is that all s-parameters is a linear stuff. I dont know how can be used in non-linear system. Can you just use large signal s-parameter for stability evaluation? As I know, there is a large signal network analyzer avaliable.