Novel comprehensive feedback theory—Part II: Unifying previous and new feedback models and further results

The objective of this Part II of the paper on a novel feedback approach is that of unifying all the previous general feedback models within a single framework and of obtaining new results. In order to pursue this goal, we exploit the multiple possibilities of implementation of the generic three-terminal circuit (TTC) that has to be inserted in the cut of the feedback loop when the cut-insertion theorem (CIT) is applied for the analysis of the network. We present models based on a direct opening of the feedback loop inside the TTC, TTC implementations (associated with circuital examples) that allow an arbitrary splitting of the signal flow between a part associated to the feedback loop and another due to a direct leakage path from input to output, and methods (with exemplifying networks) based on test signal injection that allow measuring the gain of the closed feedback loop. The asymptotic formula of the overall gain is generalized to any network. Finally, examples of application to a voltage-feedback amplifier are reported to show, in particular, the values and the properties of the multiple possible feedback loop gains that can be defined for a given cut and also to compare our results with those available in the literature.