Editing Negative-feedback amplifier (section)

{{Short description|Type of electronic amplifier}}
[[File:Block Diagram for Feedback.svg|thumb|300px|right|Figure 1: Ideal negative-feedback amplifier]]

A '''negative-feedback amplifier''' (or '''feedback amplifier''') is an [[electronics|electronic]] [[amplifier]] that subtracts a fraction of its output from its input, so that [[negative feedback]] opposes the original signal.<ref name=Kal>{{cite book |author=Santiram Kal |title=Basic Electronics: Devices, Circuits, and IT fundamentals |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+out+of+phase+with+the+input%2C+it+is+called+negative+feedback%22&pg=PA191 |pages=191 ''ff'' |isbn=978-8120319523 |publisher=Prentice-Hall of India Pvt Ltd. |year=2004  |edition=Paperback }}
</ref>  The applied negative feedback can improve its performance (gain stability, linearity, frequency response, [[step response]]) and reduces sensitivity to parameter variations due to manufacturing or environment. Because of these advantages, many amplifiers and control systems use negative feedback.<ref name=Kuo>{{cite book 
|author1=Kuo, Benjamin C.  |author2=Farid Golnaraghi
|name-list-style=amp |title=Automatic control systems
|edition=Eighth
|page=46
|year= 2003
|publisher=Wiley 
|location=NY
|isbn=0-471-13476-7 
|url=http://worldcat.org/isbn/0471134767}}
</ref>

An idealized negative-feedback amplifier as shown in the diagram is a system of three elements (see Figure 1): 
* an ''amplifier'' with [[Gain (electronics)|gain]] ''A''<sub>OL</sub>,
* a ''feedback network'' ''β'', which senses the output signal and possibly transforms it in some way (for example by [[Attenuator (electronics)|attenuating]] or [[Electronic filter|filtering]] it),
* a summing circuit that acts as a ''subtractor'' (the circle in the figure), which combines the input and the transformed output.