Editing MOSFET (section)

=== Depletion-mode ===
There are ''depletion-mode'' MOSFET devices, which are less commonly used than the standard ''enhancement-mode'' devices already described. These are MOSFET devices that are doped so that a channel exists even with zero voltage from gate to source. To control the channel, a negative voltage is applied to the gate (for an n-channel device), depleting the channel, which reduces the current flow through the device. In essence, the depletion-mode device is equivalent to a [[normally closed]] (on) switch, while the enhancement-mode device is equivalent to a [[normally open]] (off) switch.<ref>{{cite encyclopedia
 | title= Depletion Mode
 | encyclopedia= Techweb
 | date= 29 January 2010
 | location= 
 | id= 
 | url= http://www.techweb.com/encyclopedia/imageFriendly.jhtml;?term=depletion+mode
 | accessdate= 27 November 2010
 | archive-date= 31 October 2010
 | archive-url= https://web.archive.org/web/20101031061941/http://www.techweb.com/encyclopedia/imageFriendly.jhtml;?term=depletion+mode
 | url-status= dead
 }}</ref>

Due to their low [[noise figure]] in the [[RF]] region, and better [[gain (electronics)#Power gain|gain]], these devices are often preferred to [[bipolar junction transistors|bipolars]] in [[RF front end|RF front-ends]] such as in [[TV]] sets.

Depletion-mode MOSFET families include the BF960 by [[Siemens]] and [[Telefunken]], and the BF980 in the 1980s by [[Philips]] (later to become [[NXP Semiconductors]]), whose derivatives are still used in [[automatic gain control|AGC]] and RF [[frequency mixer|mixer]] front-ends.