A new approach to feedback circuit analysis called the non-ideal op amp method is proposed. The method is both accurate and simple to apply and solves the two main difficulties of the two-port analysis, namely the identification of the feedback type and the determination of the feedback network loading to the input and the output of the amplifier. The proposed methodology extends the standard op amp theory, treating every amplifier as a voltage amplifier, thus avoiding the problem of feedback type determination. All calculations refer to the unloaded open-loop circuit; therefore, there is no need to determine feedback loading. The article also demonstrates a technique for the correct calculation of the output impedance in current feedback.

feedback circuits, two-port analysis, return ratio, output impedance, loop gain