Feedback network analysis: an eclectic approach

Based on new results in circuit theory, a novel approach to feedback in linear electrical networks is proposed that generalizes the elementary one and circumvents some drawbacks and limitations that may be encountered with other general methods. It applies to all linear circuits and, differently from other approaches, does not demand two-port models or the feedback to be referred to some controlled source. Also, it evades the necessity to construct an equivalent network or to use null double injection conditions. Instead, it allows the feedback to be detected virtually in any point of the network and seems to be more effective at ‘opening the loop’ and agevolating an analysis by inspection on less complex subcircuits. Though simple and readily applicable, the present approach is rigorous, general and provides exact formulas for overall transfer functions and immittances as well as a general model of feedback. Moreover, it allows some of the most relevant achievements of other general approaches to be generalized and rederived as particular cases. Further results, such as a generalization of the virtual short-circuit method as well as a geometric interpretation of its limits of validity and of closed-loop −3 dB band limits, are achieved. Practical examples of application and comparison with other methods are also given. Copyright © 2013 John Wiley & Sons, Ltd.