Editing Feedback (section)

====Negative feedback====
Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being ''out of phase'', but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations.<ref name=Bhattacharya>
For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}
</ref> In feedback amplifiers, this correction is generally for waveform [[distortion]] reduction<ref>{{Cite web |title=Negative Feedback & Distortion |url=https://learnabout-electronics.org/Amplifiers/amplifiers34.php#:~:text=Using%20negative%20feedback%20to%20control,and/or%20cut%20off%20regions. |access-date=2024-06-07 |website=learnabout-electronics.org}}</ref> or to establish a specified [[Gain (electronics)|gain]] level. A general expression for the gain of a negative feedback amplifier is the [[asymptotic gain model]].