Remarks on the feedback interconnection of positive linear systems

Necessary and sufficient conditions for the well-posedness and stability of a particular class of closed-loop system composed by two monotone linear systems are presented and proved in this communication. The results are here reported and proved in discrete-time as well as in continuous-time. A discussion on the relations of the aforementioned conditions with other existing stability conditions, and in particular an useful interpretation (and also alternative proofs) of these reported conditions in terms of the Nyquist Stability Theorem, is included in the paper.