Negative feedback is an established technique used to improve the quality of an amplifier. The modelling of the closed-loop circuit is a complex procedure that, if not done properly, may give erroneous results. A new method for modelling amplifiers that use negative feedback over a broad frequency range is presented. The method overcomes the main difficulties of the two-port analysis, namely the identification of the feedback type and the determination of the feedback network loading to the open-loop amplifier. Compared to other methods, it is more suitable for handling frequency-dependent quantities. All topologies are treated as voltage amplifiers. The open-loop amplifier is described by three open-loop transfer functions. The theoretical context of the non-ideal op amp is used to derive the closed-loop quantities, discriminating between the non-inverting and the inverting case. The proposed method provides accurate results over a broad range of frequencies. The poles and the zeros can be readily calculated as well as the loop gain, to examine the stability of the amplifier. It can account for complex loads and frequency-dependent gain-setting resistors. Another advantage is that once the open-loop transfer functions are known, other closed-loop configurations can be computed with no additional effort. Circuit complexity has not been found to be a problem. The proposed modelling technique has been used in the class for a number of years with undergraduate students responding positively to it.
| Published in | Journal of Electrical and Electronic Engineering (Volume 10, Issue 4) |
| DOI | 10.11648/j.jeee.20221004.13 |
| Page(s) | 149-157 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
| Copyright |
Copyright © The Author(s), 2024. Published by Science Publishing Group |
Feedback Circuits, Loop-Gain, Two-Port Analysis, Return Ratio
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APA Style
Spyros Loutridis. (2022). Feedback Modelling in Amplifier Circuits Using Open-Loop Transfer Functions. Journal of Electrical and Electronic Engineering, 10(4), 149-157. https://doi.org/10.11648/j.jeee.20221004.13
ACS Style
Spyros Loutridis. Feedback Modelling in Amplifier Circuits Using Open-Loop Transfer Functions. J. Electr. Electron. Eng. 2022, 10(4), 149-157. doi: 10.11648/j.jeee.20221004.13
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Download@article{10.11648/j.jeee.20221004.13,
author = {Spyros Loutridis},
title = {Feedback Modelling in Amplifier Circuits Using Open-Loop Transfer Functions},
journal = {Journal of Electrical and Electronic Engineering},
volume = {10},
number = {4},
pages = {149-157},
doi = {10.11648/j.jeee.20221004.13},
url = {https://doi.org/10.11648/j.jeee.20221004.13},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.jeee.20221004.13},
abstract = {Negative feedback is an established technique used to improve the quality of an amplifier. The modelling of the closed-loop circuit is a complex procedure that, if not done properly, may give erroneous results. A new method for modelling amplifiers that use negative feedback over a broad frequency range is presented. The method overcomes the main difficulties of the two-port analysis, namely the identification of the feedback type and the determination of the feedback network loading to the open-loop amplifier. Compared to other methods, it is more suitable for handling frequency-dependent quantities. All topologies are treated as voltage amplifiers. The open-loop amplifier is described by three open-loop transfer functions. The theoretical context of the non-ideal op amp is used to derive the closed-loop quantities, discriminating between the non-inverting and the inverting case. The proposed method provides accurate results over a broad range of frequencies. The poles and the zeros can be readily calculated as well as the loop gain, to examine the stability of the amplifier. It can account for complex loads and frequency-dependent gain-setting resistors. Another advantage is that once the open-loop transfer functions are known, other closed-loop configurations can be computed with no additional effort. Circuit complexity has not been found to be a problem. The proposed modelling technique has been used in the class for a number of years with undergraduate students responding positively to it.},
year = {2022}
}
TY - JOUR T1 - Feedback Modelling in Amplifier Circuits Using Open-Loop Transfer Functions AU - Spyros Loutridis Y1 - 2022/07/29 PY - 2022 N1 - https://doi.org/10.11648/j.jeee.20221004.13 DO - 10.11648/j.jeee.20221004.13 T2 - Journal of Electrical and Electronic Engineering JF - Journal of Electrical and Electronic Engineering JO - Journal of Electrical and Electronic Engineering SP - 149 EP - 157 PB - Science Publishing Group SN - 2329-1605 UR - https://doi.org/10.11648/j.jeee.20221004.13 AB - Negative feedback is an established technique used to improve the quality of an amplifier. The modelling of the closed-loop circuit is a complex procedure that, if not done properly, may give erroneous results. A new method for modelling amplifiers that use negative feedback over a broad frequency range is presented. The method overcomes the main difficulties of the two-port analysis, namely the identification of the feedback type and the determination of the feedback network loading to the open-loop amplifier. Compared to other methods, it is more suitable for handling frequency-dependent quantities. All topologies are treated as voltage amplifiers. The open-loop amplifier is described by three open-loop transfer functions. The theoretical context of the non-ideal op amp is used to derive the closed-loop quantities, discriminating between the non-inverting and the inverting case. The proposed method provides accurate results over a broad range of frequencies. The poles and the zeros can be readily calculated as well as the loop gain, to examine the stability of the amplifier. It can account for complex loads and frequency-dependent gain-setting resistors. Another advantage is that once the open-loop transfer functions are known, other closed-loop configurations can be computed with no additional effort. Circuit complexity has not been found to be a problem. The proposed modelling technique has been used in the class for a number of years with undergraduate students responding positively to it. VL - 10 IS - 4 ER -
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