The Non-ideal Op Amp Method for Feedback Circuit Analysis

Spyros Loutridis^1,

¹Department of Department of Electrical and Computer Engineering, University of Thessaly, GR 383 34, Volos, Greece

Cite this paper:
Spyros Loutridis. The Non-ideal Op Amp Method for Feedback Circuit Analysis. American Journal of Electrical and Electronic Engineering. 2022; 10(1):24-31. doi: 10.12691/ajeee-10-1-3

Abstract

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.

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

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]	Millman, J. and Grabel, A, Microelectronics, McGraw-Hill, New York, 1987.
[2]	Gray, P.R., Hurst, P.J., Lewis, S.H. and Meyer, R.G, Analysis and Design of Analog Integrated Circuits, John Wiley & Sons, Inc, New York, 2001.
[3]	Sedra, S.A. and Smith, K.C, Microelectronic Circuits, Oxford University Press, 2003.
[4]	Marrero, J, “Simplified analysis of feedback amplifiers,” IEEE Trans. on Educ., 48 (1). 53-59. Feb. 2005.
[5]	Yeung, K.S, “An alternative approach for analyzing feedback amplifiers,” IEEE Trans. on Educ., 25 (4). 132-136. 1982.
[6]	Bode, H.W, Network Analysis and Feedback Amplifier Design, Van Nostrad, New York, 1945.
[7]	Rosenstark, S, “A simplified method of feedback amplifiers analysis,” IEEE Trans. on Education, 127 (4). 192-198. 1974.
[8]	Blackman, R.B, “Effect of feedback on impedance,” Bell System Technical Journal, 22. 269-277. Oct. 1943.
[9]	Hakim, S.S, Feedback Circuit Analysis, Wiley, New York, 1966.
[10]	Nicolic, B. and Marjanovic, S, “A general method of feedback amplifier analysis,” IEEE Int. Symp. Circuits Systems, Monterey, CA, 1998, 415-418.
[11]	Pellegrini, B, “Improved feedback theory”, IEEE Trans. Circuits Syst., 56 (9), 1949-1959, Sept. 2009.
[12]	Davis, A.M, “A general method for analyzing feedback amplifiers,” IEEE Trans. On Educ., E-24, 291-293, Nov. 1981.
[13]	Ochoa, A, “A systematic approach to the analysis of general and feedback circuits and systems using signal flow graphs and driving point impedance,” IEEE Trans. Circuits. Syst., 45 (2), 187-195, Feb. 1998.
[14]	Cherry, E.M, “Loop gain, input impedance and output impedance of feedback amplifiers,” IEEE Circuits and Systems Magazine, 8 (1), 55-71, first quarter 2008.
[15]	Corsi, F., Marzocca, C. and Matarrese, G, “On impedance evaluation in feedback circuits,” IEEE Trans. on Educ., 45 (4), 371-379, Nov. 2002.
[16]	Rosenstark, S, Feedback Amplifier Principles, MacMillan, New York, 1986.