A CAD tool for the small-signall stability analysis of MMIC power amplifiers

MMIC power amplifiers usually require many transistors "paralleled" by means of microstrip dividers/combiners in order to satisfy high output power requirements. Stability analysis techniques to cope with such a type of structure are quite rare in the literature while standard stability tools usually available in CAD programs are limited to single-stage or cascaded amplifiers. A simplified approach is described in this paper which is very intuitive and does not require heavy mathematical computations. The method can be applied to evaluate the stability of paralleled transistor structures, by using conventional CAD tools for microwave circuit analysis