When is a device passive?

Abstract Passivity is perhaps the most basic concept in circuit theory. Unfortunately, the existing definitions of passivity are too restrictive and often contradict one another. In this paper, a new passivity definition is proposed which is applicable to all n ‐port and ( n + 1)‐terminal devices—including time‐varying, non‐linear , and distributed circuit elements. This definition generalizes and reconciles several recent conflicting definitions.