Reappraisal of the unconditional stability criteria for active 2-port networks in terms of S parameters
Peter J. Owens, Donald J. Woods · Electronics Letters · 1970
Many different sets of stability criteria have been published, some of which are incorrect and others unnecessarily complicated. A reappraisal of the problem shows that the simplest criteria sufficient for unconditional stability are K>1 and |Δ|<1.