Feedback Amplifier Analysis: Extending the Rosenstark Method for Impedance and Noise Evaluation

We present a flexible mathematical method that extends the Rosenstark method and enables the analysis of any electrical network with feedback and all its key parameters such as gain, frequency response, input/output impedances, and noise. Unlike the original Rosenstark method, the proposed approach provides a unified procedure that can be universally applied without the need of additional steps (like Blackman’s theorem) to fully characterize the network. Our approach inherits the same advantages of the Rosenstark method, eliminating the need for approximate sub-topologies or circuit simplifications, and can be seamlessly implemented across various circuit configurations. It is thus particularly effective for analyzing amplifiers with multiple feedback loops or experimental situations involving parasitic elements that impact stability or noise. The method is useful both for experienced designers and for individuals with limited experience in circuit analysis, such as physics and engineering undergraduate students, as it relies on a minimal set of procedures to evaluate all network parameters.