Editing Amplifier (section)

{{Short description|Electronic device/component that increases the strength of a signal}}
{{About|electronic amplifiers}}
[[File:McIntosh MC2505.jpg|thumb|A [[McIntosh Laboratory|McIntosh]] stereo audio amplifier with output power of 50 watts per channel used in home component audio systems in the 1970s.<ref>[https://www.hifi-wiki.de/index.php/McIntosh_MC_2505 HiFi-Wiki webpage with facsimile] of data sheet</ref>]]
 
[[File:Amplification2.svg|thumb|''Amplification'' means  increasing the [[amplitude]] (voltage or current) of a time-varying signal by a given factor, as shown here. The graph shows the input <math>v_i(t)</math> ''<span style="color:blue;">(blue)</span>'' and output voltage <math>v_o(t)</math> ''<span style="color:red;">(red)</span>'' of an ideal linear amplifier with an arbitrary signal applied as input.   
In this example the amplifier has a ''[[gain (electronics)|voltage gain]]'' of 3; that is at any instant <math>v_o(t) = 3v_i(t)\,</math>]]

An '''amplifier''', '''electronic amplifier''' or (informally) '''amp''' is an electronic device that can increase the magnitude of a [[Signal (information theory)|signal]] (a time-varying [[voltage]] or [[Electric current|current]]).  It is a [[two-port network|two-port]] electronic circuit that uses electric power from a [[power supply]] to increase the [[amplitude]] (magnitude of the voltage or current) of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its [[gain (electronics)|gain]]: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a [[power gain]] greater than one.<ref name="Crecraft">{{cite book| last1  = Crecraft| first1 = David| last2  = Gorham| first2 = David| title  = Electronics, 2nd Ed.| publisher = CRC Press| date   = 2003| pages  = 168| url    = https://books.google.com/books?id=Yq66DDW4f8IC&q=amplifier+power&pg=PA168| isbn   = 978-0748770366}}</ref><ref name="Agarwal">{{cite book | last1  = Agarwal| first1 = Anant  | last2  = Lang  | first2 = Jeffrey | title  = Foundations of Analog and Digital Electronic Circuits| publisher = Morgan Kaufmann| date   = 2005| pages  = 331| url    = https://books.google.com/books?id=lGgP7FDEv3AC&q=amplifier+power&pg=PA331| isbn   = 978-0080506814}}</ref><ref name="Glisson">{{cite book | last1  = Glisson | first1 = Tildon H. | title  = Introduction to Circuit Analysis and Design | publisher = Springer Science and Business Media | date   = 2011 | url    = https://books.google.com/books?id=7nNjaH9B0_0C&q=amplifier+power&pg=PA197 | isbn   = 978-9048194438}}</ref>

An amplifier can be either a separate piece of equipment or an [[electrical circuit]] contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the [[frequency]] of the electronic signal being amplified. For example, [[audio amplifier]]s amplify signals of less than 20&nbsp;kHz, radio frequency (RF) amplifiers amplify frequencies in the range between 20&nbsp;kHz and 300&nbsp;GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. Amplifiers can also be categorized by their physical placement in the [[signal chain]]; a [[preamplifier]] may precede other signal processing stages, for example,<ref name="Patronis">{{cite book |last=Patronis |first=Gene |chapter=Amplifiers |editor=Glen Ballou |title=Handbook for Sound Engineers: The New Audio Cyclopedia |year=1987 |publisher=Howard W. Sams & Co. |isbn=978-0-672-21983-2 |page=493}}</ref> while a power amplifier is usually used after other amplifier stages to provide enough output power for the final use of the signal. The first practical electrical device which could amplify was the [[triode]] [[vacuum tube]], invented in 1906 by [[Lee De Forest]], which led to the first amplifiers around 1912. Today most amplifiers use [[transistor]]s.