A Feedback Model for Active n-Port Networks Derived from a Concept of Port Orientation

Beginning with fundamental observations, the concept of port orientation is introduced providing a classification of networks as oriented or nonoriented. By incorporating the orientation property in the network mathematical description, a feedback model equivalent to active networks is derived. In this way the stability criteria of feedback systems can be directly applied to active networks. The feedback model is applied to the stability study of negative resistance 1-ports, negative impedance converters, and negative impedance inverters. It is shown that the observed stability behavior can be systematically derived without explicitly including the device parasitics. Accordingly, the identity of the negative impedance converter ports as opencircuit stable or closed-circuit stable becomes systematically available.