Editing Regenerative circuit (section)

{{Short description|Electronic circuit using positive feedback}}
{{Other uses |Heat exchanger#Regenerative heat exchanger}}
[[File:Regenerartive Receiver-S7300059.JPG|250px|thumb|Homebuilt Armstrong one-tube regenerative [[shortwave]] radio with construction characteristic of the 1930s - 40s. The controls are ''(left)'' regeneration, ''(lower center)'' filament rheostat, ''(right)'' tuning capacitor.]]
[[File:Regenerartive Receiver-S7300056.JPG|250px|thumb|Rear view of the above radio, showing the simplicity of the regenerative design.  The tickler coil is visible inside the tuning coil and is turned by a shaft from the front panel; this type of adjustable transformer was called a ''[[variocoupler]]''.]]

A '''regenerative circuit''' is an [[amplifier]] circuit that employs [[positive feedback]] (also known as '''regeneration''' or '''reaction''').<ref>[https://books.google.com/books?id=lROa-MpIrucC&pg=PA265 S. W. Amos, R. S. Amos, ''Newnes Dictionary of Electronics'', 4th ed., London, U. K.: Newnes, 1999, p. 265, 269]</ref><ref>[https://archive.org/stream/ThermionicValveCircuits/Williams-ThermionicValveCircuits#page/n161  E. Williams, ''Thermionic Valve Circuits'', 4th ed., London: Sir Isacc Pitman & Sons, 1961, p. 151]</ref> Some of the output of the amplifying device is applied back to its input to add to the input signal, increasing the amplification.<ref name="Everitt01">[https://archive.org/details/communicationeng00ever W. L. Everitt, ''Communication Engineering'', 2nd ed. New York: McGraw-Hill, 1937, p. 463]</ref> One example is the [[Schmitt trigger]] (which is also known as a '''regenerative comparator'''), but the most common use of the term is in [[Radio Frequency|RF]] amplifiers, and especially '''regenerative receivers''', to greatly increase the [[gain (electronics)|gain]] of a single amplifier stage.<ref>[https://www.americanradiohistory.com/Archive-Bookshelf/Technology/The-Manual-Of-Modern-Radio-John%20Scott-Taggart.pdf J. Scott-Taggart, ''The Manual of Modern Radio'', London: The Amalgamated Press LTD., 1933, p. 94]</ref><ref name="TM11-665">{{cite book   
  | title = Technical Manual TM 11-665: C-W and A-M Radio Transmitters and Receivers
  | publisher = Dept. of the Army, US Government Printing Office
  | date = 1952
  | pages = 187–190
  | url = https://books.google.com/books?id=f9QXAAAAYAAJ&pg=PA187
  }}</ref><ref name="Poole">{{cite book   
  | last = Poole
  | first = Ian 
  | title = Basic Radio: Principles and Technology
  | publisher = Newnes
  | date = 1998
  | pages = 100
  | url = https://books.google.com/books?id=vaUGlb_Gd18C&q=regenerative+receiver&pg=PA100
  | isbn = 0080938469}}</ref>

The regenerative receiver was invented in 1912<ref>{{cite web
  | first = Sungook
  | last =  Hong
  | title = A history of the regeneration circuit: From invention to patent litigation
  | publisher = Institute of Electrical and Electronics Engineers
  | url = https://aireradio.org/Superet_arms/storia%20della%20reazione.pdf
  | access-date = March 9, 2014}}</ref> and patented in 1914<ref name="ArmstrongPatent" >US Patent 1113149A, Edwin H. Armstrong, ''[https://patents.google.com/patent/US1113149?oq=Edwin+armstrong    Wireless receiving system]'', filed October 29, 1913, granted October 6, 1914</ref> by American electrical engineer [[Edwin Armstrong]] when he was an undergraduate at [[Columbia University]].<ref name="Armstrong">{{cite journal 
|last=Armstrong 
|first=Edwin H. 
|title=Some recent developments in the Audion receiver 
|journal=Proc. IRE 
|volume=3 
|issue=9 
|pages=215&ndash;247 
|publisher=[[Institute of Radio Engineers]] 
|location=New York 
|date=September 1915 
|doi=10.1109/JRPROC.1915.216677 
|s2cid=2116636 
|url=http://www.ieee.org/documents/00573757.pdf
|archive-url=https://web.archive.org/web/20130728164117/http://www.ieee.org/documents/00573757.pdf
|url-status=dead
|archive-date=July 28, 2013
|access-date=August 29, 2012 
}}</ref> It was widely used between 1915 and [[World War II]]. Advantages of regenerative receivers include increased sensitivity with modest hardware requirements, and increased selectivity because the [[Q factor|Q]] of the tuned circuit will be increased when the amplifying vacuum tube or transistor has its [[feedback loop]] around the tuned circuit (via a "tickler" winding or a tapping on the coil) because it introduces some [[negative resistance]].

Due partly to its tendency to radiate interference when oscillating,<ref name="Poole" /><ref name="TM11-665" />{{rp|p.190}} by the 1930s the regenerative receiver was largely superseded by other [[Tuned radio frequency receiver|TRF]] receiver designs (for example [[Reflex receiver|"reflex" receivers]]) and especially by another Armstrong invention - [[superheterodyne receiver]]s<ref name="Malanowski">{{cite book   
  | last = Malanowski
  | first = Gregory 
  | title = The Race for Wireless: How Radio Was Invented (or Discovered?)
  | publisher = AuthorHouse
  | date = 2011
  | pages = 66
  | url = https://books.google.com/books?id=IAjtEeVtXqAC&q=regeneration+radio&pg=PA79
  | isbn = 978-1463437503}}</ref> and is largely considered obsolete.<ref name="TM11-665" />{{rp|p.190}}<ref name="Williams">{{cite book   
  | last = Williams
  | first = Lyle Russell 
  | title = The New Radio Receiver Building Handbook
  | publisher = Lulu
  | date = 2006
  | pages = 24–26, 31–32
  | url = https://books.google.com/books?id=XiKgKdeBi6cC&q=%22regenerative&pg=PA25
  | isbn = 1847285260}}</ref> Regeneration (now called positive feedback) is still widely used in other areas of electronics, such as in [[electronic oscillator|oscillators]], [[active filter]]s, and [[Bootstrapping (electronics)|bootstrapped amplifiers]].

A receiver circuit that used larger amounts of regeneration in a more complicated way to achieve even higher amplification, the  '''superregenerative receiver''', was also invented by Armstrong in 1922.<ref name="Williams" /><ref name="TM11-665" />{{rp|p.190}} It was never widely used in general commercial receivers, but due to its small parts count it was used in specialized applications. One widespread use during WWII was [[identification friend or foe|IFF]] [[transceiver]]s, where single tuned circuit completed the entire electronics system. It is still used in a few specialized low data rate applications,<ref name="Williams" /> such as [[garage door opener]]s,<ref name="Bensky">{{cite book   
  | last = Bensky
  | first = Alan  
  | title = Short-range Wireless Communication: Fundamentals of RF System Design and Application
  | publisher = Newnes
  | date = 2004
  | pages = 1
  | url = https://books.google.com/books?id=AoF1asCDbNgC&q=%22superregenerative+receiver&pg=PA1
  | isbn = 008047005X}}</ref> [[wireless networking]] devices,<ref name="Williams" /> [[walkie-talkie]]s and toys.