Talk:Field-effect transistor

message: The schematic for your MOSFET shows a solid line connecting the Source and Drain. Does this not indicate a depletion mode MOSFET?.  An enhancement mode MOSFET is symbolically shown with a dashed line between the Source and Drain.
The arrows for the 'metallurgical' contacts point at the bottom of the N diffusions.  The metal contact is on the top surface.  Shouldn't your arrows point to the upper surface of the N regions?.
:All textbooks use different notations.  I can't remember right now what is right, and what is depletion, enhancement, etc...  However, should use standard IEEE conventional symbols, whatever those are, and we should state that they are the IEEE standard symbols.  If there are some common "misuses" of the symbols out there, then we should mention that.  So first thing I think is to check IEEE and see if there are standard symbols, and secondly to check something like Art of Electronics and see what it uses.  dave 22:06, 16 Oct 2003 (UTC)
replies: text:  You are right about the 'metallurgical' junctions, they are on top of the diffusion region and are not the same! Modern FETs do not only use high doping, but also metal silicides at this place.--Qdr 17:12, 17 Jul 2004 (UTC)
thread_title:  mosfet symbols 

message: Near the top, the article says "depletion, in which a voltage applied decreases the current flow from source to drain." This isn't true, is it? I think whoever wrote that sentence was confusing the difference between n-channel and p-channel, with the difference between enhancement mode and depletion mode. It would be more accurate to say "enhancement mode, which is normally off, when zero voltage is applied, and depletion mode, which is normally on, when zero voltage is applied." Objections to this change?  --Monguin61 17:55, 4 March 2006 (UTC)
replies: text: It's true depending on what definitions are used, but it's definitely not clear. It's hard to make things both accurate and accessible. How do you define "when zero voltage is applied" without making things too complicated? - mako 03:30, 5 March 2006 (UTC)
replies: text: I think "normally off" and "normally on" should suffice. That's more towards the accessible side than accurate, but more accurate than the current phrasing, yes? --66.253.212.165 08:09, 7 March 2006 (UTC)
thread_title:  Behavior of d mode FETs 

message: I have recently been investigating the process by which a PIN diode can modulate a signal as a result of incident radiation.  My main point of confusion has been my inability to find any mechanical diagrams of a PIN diode which operates through the presence of 3 terminals.  Most of what I have read suggests that this is a strictly 2-terminal device (the PIN in question, a Hamamatsu S5971).  I came across a diagram for a FET, and was struck by not only the presence of the proper number of terminals, but the drain signal's dependence on variations in the space charge region.  I am mainly curious as to the possibility that my PIN may be closer in design to an FET, through the use of the intrinsic region as the source of the drain terminal.  Whether this is may be a step in the proper direction or its equally likely counterpart, I would appreciate any insight that may be offered on the subject.  Jmeyers 18:39, 10 May 2006 (UTC)
thread_title:  Field Effect Transistors as Light Detectors 

message: I'd like seconding by someone more expert than myself before making any changes; The article says (Para 5 of section 'FET Operation'); "The shape of the inversion region becomes "pinched-off" near the drain end of the channel". Unless I am mistaken, when a positive potential difference is applied between D and S the pinch region is at the source end of the channel, as the potential difference pulls the charge carriers in the inversion region (the electrons) closer to the drain (positive potential). This is corroborated by my own knowledge as well as (not explicitly) here. Comments please, Spychotic (talk)
This is not an error actually.  Channel starts pinching off near Drain side first due to the voltage drop in the channel itself.--Murat (talk) 19:31, 22 November 2009 (UTC)
replies: text: Moreover, the original poster is only half wrong. The positive potential at the drain is the reason for the pinch off. However, it is not pulling carriers from the inversion region toward the drain. Instead, it is holding carriers already in the drain to limit their entry into the inversion region. Hence, the source contributes more carriers to the inversion region than the drain, and so the channel's shape is asymmetric with a "wide bottom" near the source. (so the confusion seems to be about where the carriers in the inversion region "came from"; in an enhancement-mode FET, their "home" is in the source and drain) —TedPavlic (talk/contrib/@) 19:26, 23 November 2009 (UTC)
thread_title:  Saturation explanation error? 

message: I keep seeing references to "FETs" as an ancient predecessor to MOSFETS et al described herein.  What kind of FET is one referring to then? -143.215.155.50 (talk) 03:55, 10 October 2008 (UTC)
replies: text: How about to a reference to where you're seeing this?  Doesn't sound familiar. Dicklyon (talk) 05:06, 10 October 2008 (UTC)
thread_title:  FET? 

message: Why is there no FET history section?  When and how was the FET created?  -143.215.155.50 (talk) 03:55, 10 October 2008 (UTC)
replies: text: I added a brief history section with a main link to the history of the transistor article. Dicklyon (talk) 05:07, 10 October 2008 (UTC)
thread_title:  History?? 

message: There is a lack of information regarding the physics of channel inversion ... that is when the p type semiconductor has an n type channel formed under the gate. The statemant below is wrong.. the phenomenom is not called the threshold voltage, threshold is just the voltage at which this occurs and current begins conducting through the channel... the phenomenom is called inversion. 
"..........; this forms a region free of mobile carriers called a depletion region, and the phenomenon is referred to as the threshold voltage of the FET. "  —Preceding unsigned comment added by Jonnic1 (talk • contribs) 10:02, 29 January 2009 (UTC)
replies: text: Agreed. That section needs major copyedits or perhaps a complete rewrite. For exampel, the terms threshold voltage, inversion, and depletion should all be used, but they should not necessarily all be used in the same sentence. The section should more carefully discuss inversion. —TedPavlic (talk) 16:41, 29 January 2009 (UTC)
thread_title: lack of explanation of the inversion layer formation

message: A new Transistor channel page was recently created. After some discussion on its talk page, the original author changed it to a redirect to a FET subsection and moved the original content to Talk:Transistor channel/draft. Please review that page (with emphasis on the discussion in the talk page). The author feels that transistor channels are not adequately handled on the FET page and feels that the subject is rich enough to warrant a separate page.
I'm not quite sure I understand the argument, as a detailed discussion of the operation of unipolar channels seems identical to a detailed discussion of FET operation. So perhaps the FET page needs to be enhanced. Either way, the page was created and a discussion was started, and I think people who read this page would be interested. —TedPavlic (talk) 14:05, 29 January 2009 (UTC)
replies: text: And I advised the new editor that if he doesn't get consensus here, he may find it merged back when he's done.  I'm undecided on which way to go (enhance this page, or deplete it to a split).  Dicklyon (talk) 16:28, 29 January 2009 (UTC)
replies: text:  In retrospect, the existence of a page like "threshold voltage" is a precedent for creating more such small pages. I just worry that these small pages are really just trying to fill in information that belongs to the FET page. The MOSFET page is very long and developed (and is a much better page than the FET page), and it probably describes unipolar operation much better than anything here. In a perfect world, I think a completely rewrite of the FET page would not only alleviate the need for pages like "threshold voltage" (and transistor channel) but would allow other FET pages (like MOSFET and JFET and MESFET) to be shorter/clearer. ON THE OTHER HAND, having very generic threshold voltage–type pages might make it easier to make pages like MOSFET more concise because each FET page could share wiki links to things they have in common. So I'm torn... But I think the current transistor channel work looks more like a FET rewrite, and so it maybe should be here... I think... Hm. —TedPavlic (talk) 16:45, 29 January 2009 (UTC)
replies: text: MOSFET is at about 40 KB, and transistor at 64 KB, large compared to suggested article size.  Splits like these can be useful in allowing room to develop the subtopic.  The threshold voltage article is not bad, has a half dozen refs.  If the transistor channel gets to that point, it might be OK.  Dicklyon (talk) 17:31, 29 January 2009 (UTC)
thread_title:  New "Transistor channel" page 

message: I think this sentence contains errors. Anybody else?
"The drain and source may be doped of opposite type to the channel, in the case of enhancement mode FETs, or doped of similar type to the channel as in depletion mode FETs." 
User:Vanished user 8ij3r8jwefi 15:39, 23 October 2009 (UTC)
thread_title:  Sentence suspected having errors 

message: Perhaps the brand new NOMFET (nanoparticle organic memory field-effect transistor) should be added.
See: http://www.physorg.com/news183373216.html
Codegrinder (talk) 21:56, 1 February 2010 (UTC)
thread_title:  NOMFET 

message: Prior content in this article duplicated one or more previously published sources.  Copied or closely paraphrased material has been rewritten or removed and must not be restored, unless it is duly released under a compatible license. (For more information, please see "using copyrighted works from others" if you are not the copyright holder of this material, or "donating copyrighted materials" if you are.) For legal reasons, we cannot accept copyrighted text or images borrowed from other web sites or published material; such additions will be deleted. Contributors may use copyrighted publications as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously, and persistent violators will be blocked from editing. While we appreciate contributions, we must require all contributors to understand and comply with these policies. Thank you.  Osiris (talk) 04:00, 23 June 2012 (UTC)
replies: text: Duplication report:  Osiris (talk) 04:00, 23 June 2012 (UTC)
thread_title:  Copyright problem removed 

message: I don't know enough to make appropriate corrections, but I presume BJT refers to Bipolar Junction Transistors? It would be nice if the abbreviation was introduced and the reason that they are mentioned alongside Field Effect transistors was made clear.  — Preceding unsigned comment added by 128.197.40.40 (talk) 14:32, 24 September 2012 (UTC)
thread_title:  BJT mentioned six times without being explained 

message: Would be useful to have an image showing the common circuit symbols for a FET (at least it would have been for myself who had to do a separate search on google images after finding the wikipedia page) Norlesh (talk) 11:05, 14 March 2014 (UTC)
replies: text: Yes! It's rather remarkable that we don't have them already. The symbols for JFETs and MOSFETs would be useful to distinguish, also to explain details like the source-body internal tie. There's (surprisingly) nothing on Commons that I can see. Please use SVG if you create one, as the scalability would be useful. Andy Dingley (talk) 11:44, 14 March 2014 (UTC)
thread_title:  Circuit schematic symbol for a FET 

message: Hello fellow Wikipedians,
I have just added archive links to  on Field-effect transistor. Please take a moment to review my edit. If necessary, add  after the link to keep me from modifying it. Alternatively, you can add  to keep me off the page altogether. I made the following changes:
*Added archive https://web.archive.org/20080706162027/http://www.ece.cmu.edu/~cssi/research/manufacturing.html to http://www.ece.cmu.edu/~cssi/research/manufacturing.html
*Added archive http://web.archive.org/web/20160105144331/http://www.analog.com/library/analogDialogue/archives/35-05/latchup/ to http://www.analog.com/library/analogDialogue/archives/35-05/latchup/
*Added archive http://web.archive.org/web/20100116183339/http://freespace.virgin.net:80/ljmayes.mal/comp/vcr.htm to http://freespace.virgin.net/ljmayes.mal/comp/vcr.htm
When you have finished reviewing my changes, please set the checked parameter below to true to let others know.
Cheers.—cyberbot IITalk to my owner:Online 16:38, 26 February 2016 (UTC)
thread_title:  External links modified 

message: Hi guys, I'm new to the topic, and from this article (and all the others article on Wikipedia related to transistors), there is no clear explanation of the role of the body in FETs. An explanation in the section More about terminals would be greatly appreciated! Piero le fou (talk) 19:03, 19 April 2016 (UTC)
replies: text: A good way to think of the body's effect on the operation of the transistor (in normal operating regions) is as a "back gate" terminal (e.g. see this book).  It works just like the gate, though typically a bit less efficiently, as long as you keep the source–bulk and drain–bulk junctions reverse biased.  See Threshold voltage#Body effect.  Years ago I tried to say something more sensible in the article, but Brews-ohare wouldn't let me.  We compromised, but it's fuzzy.  I'll see what I can dig up.  Dicklyon (talk) 20:46, 19 April 2016 (UTC)

text: For example, in this paper, we used the reduced efficiency of the bulk as a gate to make a differential amplifier with lower gain and wider input linear range; the inputs come directly into the body terminals of two transistors, and nowhere else.  Dicklyon (talk) 20:54, 19 April 2016 (UTC)
thread_title:  Request for explanation on role of 'body' 

message: A recent edit by 50.48.192.249 changed a statement about non-FET's being current controlled to voltage controlled devices. I feel like this should either be explained in more detail. From my knowledge of the matter, a BJT being voltage or current controlled depends on the "depth" one is willing to go and neither is strictly right or wrong. From an external perspective, yes, (in an NPN device) the voltage applied to the base-emmitor junction causes a current to flow in this PN junction. But on a "deeper" level, when you look at the junction physics, it is the electrons flowing from the emitor to the base that can then get "into" the collector before recombining in the base (asumming the base is small enough) causing a current from the collector to the emittor. 
In other words, a BJT cannot be boxed in as being purely "voltage" or "current" controlled, because unlike most FET's, which have a very high (and often assumed infinite) input impedance at low frequencies, making it clearly a voltage-controlled device, the BJT has a non-zero, and finite imput impeadance. In other words, It's not really a pure voltage or current controlled device. 
I bring this up because I feel like this should be discussed in more detail to prevent a constant to and fro in the article. TheUnnamedNewbie (talk) 13:46, 25 January 2017 (UTC)
replies: text: On a second read through the introduction, I feel like maybe the entire statement should just be removed. I think it's not really valid to speak of "all of the non-FET devices", as it implies that there are only two categories of devices, the FET's and the non-FET's. TheUnnamedNewbie (talk) 13:50, 25 January 2017 (UTC)
replies: text:  I edited the introduction to remove the "voltage" or "current" controlled statements. After thinking about it I felt like they could be misleading as they imply there is a "input" and an "output" terminal, which is not really the case (eg, common gate transistors in cascodes?). I'm open for counter arguments. 
I also simplified it somewhat to not go into as much depth in the introduction. TheUnnamedNewbie (talk) 10:39, 28 January 2017 (UTC)
thread_title:  BJT as Voltage or Current controlled device 

message: I corrected this in section #Effect of gate voltage on current. Even with the correction, the phrasing is poor and contains true but unnecessary information, given the purpose of the section. I'm not sure I'm qualified to edit it further.
"In a p-channel "depletion-mode" device, a positive voltage from gate to body creates a depletion layer by forcing the positively charged holes to the gate-insulator/semiconductor interface, leaving exposed a carrier-free region of immobile, negatively charged acceptor ions."  — Preceding unsigned comment added by 173.127.144.113 (talk) 07:33, 18 June 2018 (UTC)
thread_title:  Check me 

message: The History section states the FET was "first patented *** in 1925", but the patent was not filed until 8 October 1926 and not issued until 28 January 1930 as shown in the approval document cited. How should the Wikipedia text be changed: to reflect the year the patent was granted or the year of filing (more interesting)... assuming the "1925" is a mistake. Myron (talk) 23:31, 12 February 2021 (UTC)
replies: text: https://en.wikipedia.org/wiki/History_of_the_transistor#Origins_of_transistor_concept 176.52.34.12 (talk) 12:20, 14 April 2024 (UTC)
thread_title:  Date of Lilienfeld's FET concept patent 

message: https://www.quora.com/Can-the-drain-and-source-of-a-MOSFET-be-interchangable/answer/Jeff-Gruszynski
This answer (which looks detailed and coherent) says that MOSFETs as used in CMOS are not symmetrical.
The "Uses" section of the article currently says "The naming convention of drain terminal and source terminal is somewhat arbitrary, as the devices are typically (but not always) built symmetrical from source to drain."
If the Quora answer is correct, then the "Uses" section should be clarified.
Cphoenix (talk) 21:16, 30 May 2022 (UTC)
replies: text: I agree with Cphoenix. This statement does not seem to be correct: "The source and drain terminals can thus be interchanged in practical circuits with no change in operating characteristics or function". Aren't the differences between eg common-drain and common-source topologies due to MOSFETs being controlled by their gate-source voltage (Vgs)? In practical circuits, at least DC circuits, flipping source and drain will result in a nonworking circuit because the polarity of Vgs changes. 209.160.150.130 (talk) 21:00, 7 September 2023 (UTC)
thread_title:  Are FETs source/drain symmetrical?