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Understanding Loading In Feedback Amplifier Analysis

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2003 Annual Conference


Nashville, Tennessee

Publication Date

June 22, 2003

Start Date

June 22, 2003

End Date

June 25, 2003



Conference Session

Electrical and Computer Engineering

Page Count


Page Numbers

8.1222.1 - 8.1222.9



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Paper Authors

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Manuel Toledo-Quinones

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 1532

Understanding Loading in Feedback Amplifier Analysis Manuel Toledo-Quiñones Electrical and Computer Engineering Department University of Puerto Rico Mayagüez, Puerto Rico

Introduction The application of negative feedback concepts to the analysis and design of electronic amplifiers is widely recognized as one of the most important subjects in electrical engineering curricula. Most electrical engineering students are exposed to feedback theory in courses primarily focused on systems and automatic controls. However, instructors teaching analog electronic circuits courses still devote considerable time explaining how to analyze feedback amplifiers because many practical aspects, such as the consideration loading effects, do not show up in other courses.

This paper presents some examples that illustrate some aspects of feedback amplifier analysis related to the correct use of input and output impedances. It is the author´s experience that the relevant material normally found in undergraduate textbooks on microelectronics does not illustrate how to properly use these quantities. The objective of this paper is to provide educators with an additional tool to clarify these aspects of the subject.

Overview of the Feedback Method An ideal feedback amplifier can be represented by the block diagram shown in figure 1. The quantities ωs , ωi , ωo and ωf represent the source, amplifier input, amplifier output and feedback signal, and can be voltages or currents. Amplifiers are classified according to the type of signal (voltage or current) being sampled at the output and mixed at the input. The four feedback configurations are shown in figure 2. The naming convention used in this article is summarized in table 1.

amplifier ωS ωi ωo A ωF

β feedback network

Figure 1: Ideal feedback amplifier, composed of a non-feedback amplifier and a feedback network.

Proceedings of the 2003 American Society for Engineering Education Annual Conference & Exposition Copyright c 2003, American Society for Engineering Education

Toledo-Quinones, M. (2003, June), Understanding Loading In Feedback Amplifier Analysis Paper presented at 2003 Annual Conference, Nashville, Tennessee. 10.18260/1-2--12516

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