Novel Feedback Theory of Electric Circuits—Part II: Loop Invariants

In this paper and in its companion, a novel cut-based decomposition for transfer functions of linear time-invariant circuits is introduced and an invariance property, with respect to the cut, is proven for the set of quantities introduced by this cut-based decomposition. These results naturally lead to a novel feedback theory of electric circuits which, unlike Bode's feedback theory, is based on the unambiguous decomposition of transfer functions. Such feedback theory provides a natural extension to the elementary model of feedback amplifiers based on block diagrams, from system theory to circuit theory, and a natural extension to Blackman's formula.