Stability of an Active Two Port Network in terms of S Parameters

Yoshihiro MIWA

IEICE TRANSACTIONS on Electronics   Vol.E77-C    No.3    pp.498-509
Publication Date: 1994/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electronic Circuits
stability,  active two-port network,  S-parameters,  microwave amplifier,  

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The stability conditions and stability factors of terminated active two port networks are investigated. They are expressed with the S parameters of active devices and the radii and centers of the circles defined by source and load terminations. The stability conditions are applied to specific cases. Some of the results correspond to the stability conditions expressed in Z, Y, H or G parameters and one of the other stability conditions of terminated two port network is similar to that for passive terminations which is expressed in S parameters. The various results derived in this paper are very useful for checking the stability of amplifiers, because both stability conditions and stability factors are simply calculated by using the S parameters without using the graphical method or transforming S parameters to Z, Y, H or G parameters. These stability conditions can be also used even if negative input or output resistance appears and even if the real part of source or load immittance is negative.