Talk:Bipolar junction transistor

message: Were most germanium transistors, PNP transistors? Were NPN germanium transistors uncommon? 24.26.128.185 (talk) 22:07, 25 April 2008 (UTC)
thread_title:  Polarity of germanium transistors 

message: If the positive voltage is less than 0.6V for a silicon BJT, the junction does not have enough voltage to forward bias it, and no current will flow.  The sentence should read "when a current flows between the base and emitter.." or "..if enough positive voltage is applied to the base-emitter junction to cause a current to flow..".  One has to remember that the BJT is a current operated device.
July 25, 2012 by Watson - my yahoo email account is acmefixer. Acmefixer (talk) 14:59, 25 July 2012 (UTC)
thread_title:  "..when a positive voltage is applied to the base–emitter junction.." 

message: The link www.brookdale.cc.nj.us/fac/engtech/aandersen/engi242/bjt_models.pdf should be updated to a new location or removed.  —Preceding unsigned comment added by 130.225.243.80 (talk) 20:31, 10 August 2008 (UTC)
replies: text: The correct (new) URL appears to be http://ux.brookdalecc.edu/fac/engtech/andy/engi242/bjt_models.pdf. --TedPavlic | (talk) 20:46, 11 September 2008 (UTC)
thread_title:  external reference bjt_models.pdf gone 

message: the following section was deleted on may 20, only one day after it went up:
"A simple model with many of the properties of a transistor, especially a phototransistor, is a forward biased LED (emitter–base junction) and a reverse biased photodiode (base–collector junction) sharing an anode (base) in a single package so that 99% (1-1/βF) of the photons emitted by the LED are absorbed by the photodiode. Each electron-hole recombination in the LED produces one photon and each photon absorbed by the photodiode produces one electron-hole pair therefore each electron injected into the base would result in 100 (βF) electrons at the collector". 
I will leave this copy here so others can discuss whether it should or should not be included in the article. just-emery (talk) 16:25, 20 May 2009 (UTC)
replies: text: This is a complicated passage, and it would take me a lot of time to figure out if this is a useful model or not. Things that require serious thoughts by people experienced in the field to figure out should not be made up by Wikipedia editors; they should come from reliable published sources. --Jc3s5h (talk) 16:35, 20 May 2009 (UTC)
replies: text: It is trivial. If you think its complicated then you are in no position to be judging it.  I do not claim that it has all of the properties of a transistor but it obviously does amplify the current. Any high school freshman can see that. just-emery (talk) 16:40, 20 May 2009 (UTC)
replies: text: Go read Wikipedia:Verifiability. Since you have no source for this, I will resist the inclusion of this passage. Remember, you may think you are an expert, you may even be an expert, but Wikipedia readers have no way to know who you are. --Jc3s5h (talk) 17:12, 20 May 2009 (UTC)
replies: text: You are trying to confuse the issue. The issue is why on earth  this trivial model, which obviously works and makes it easy for beginners to understand (which is what wikipedia is supposed to be about) the operation of the transistor, should be excluded from the article. just-emery (talk) 06:22, 22 May 2009 (UTC)

text: 10,000 electrons injected into the base results in 10,000 electrons appearing at the collector and 10,000 photons created by the led. 9900 of the photons are absorbed by the photodiode which creates 9900 more electrons which travel to the LED and create 9900 more photons and then the electrons move on to the colloctor. 9801 photons are then absorbed by the photodiode. and so on. in the end 100*10,000 electrons reach the collector.  100 times more than was initially injected. 100 fold amplification. just-emery (talk) 06:22, 22 May 2009 (UTC)
replies: text:  It's unclear to me how this example aids in the understanding of a bipolar transistor. That is, would a novice who could grok this example easily be able to transition to the more accurate descriptions of diffusion and drift currents? After all, this sort of feedback process cannot be described so explicitly in a BJT (try giving such a feedback explanation WITHOUT using photons). In a BJT, a field is used to turn off the natural dipole that is created by bipolar diffusion; without the dipole, the diffusion can continue and the BJT acts like a current source (where the voltage it displaces is ohmic loss across the base–collector depletion region that narrows and widens as necessary). That's not only the conventional way of understanding bipolar operation, but it is not that technical. We should stick to conventional explanations that can be found in trusted sources (e.g., textbooks). If you think your photon model is a compelling way of explaining BJTs, you should try to find it in an existing textbook and reference it. If you can't find it, you should submit your novel example to a textbook writer. When your example comes out in print, then some other Wikipedia editor will be able to use it and reference it. —TedPavlic (talk) 13:00, 22 May 2009 (UTC)
replies: text: The purpose of a model is simplicity, not accuracy. just-emery (talk) 15:15, 26 May 2009 (UTC)
replies: text: Your model lacks both simplicity and accuracy, and that's what makes it misleading. You are building fictitious behaviors on top of existing sophisticated devices, namely photodiodes and p–n junctions. You cannot be so cavalier as an encyclopedia editor because readers of the encyclopedia count on you to reflect information that can be verified by a large consensus of experts in the field. There is a great risk that someone may misread your highly inaccurate description as a statement of fact. In the end, the essence of your description is that a transistor provides amplification. There is no reason to posit some mechanism for that amplification if it is not the actual mechanism being used. —TedPavlic (talk) 17:15, 26 May 2009 (UTC)
thread_title:  A simple model of the transistor consisting of an LED and a photodiode 

message: The BJT is a minority carrier device because most of the charge cariers passing through the control region, the base, are minority carriers with respect to the base. However, it is wrong to say it is a minority carrier device on account of the base current, becase "base current" is taken to mean the current in or out of the base terminal. The base terminal current is not what gets the job done (in the active region); the job gets done by the collector and/or emitter current. Therefore the classification of the device is based on the collector or emitter current. --Jc3s5h (talk) 00:15, 29 June 2009 (UTC)
replies: text: I see. So "base current" to you refers to the current coming out of the base rather than the large concentration of minority carrier current going up from the base into the collector. Well, you're the boss. Revised. —TedPavlic (talk) 15:58, 29 June 2009 (UTC)
replies: text: That's true; base current is defined as the current into the base terminal.  The collector current can perhaps be called the base–collector current, which is what you probably meant to refer to.  Dicklyon (talk) 07:06, 30 June 2009 (UTC)
thread_title: Minority carrier device

message: There is a miror error on the figure associated with the section entitled, "Active-mode PNP transistors in circuits". The arrow indicating the directional flow of the base current "Ib" should point away from the transistor, not toward it.  —Preceding unsigned comment added by 199.181.136.59 (talk) 15:49, 1 July 2009 (UTC)
thread_title:  Active-mode PNP transistors in circuits figure incorrect 

message: As one who can barely understand the technobabble on the page, ;D can somebo clarify: is the point-contact design mentioned the same as (or equivalent to) what I've seen described as a "cuprous-contact rectifier"? If not, how do they differ? ("In English, McGee.")  TREKphiler hit me ♠  09:37, 20 November 2009 (UTC)
thread_title: The $6 Man

message: Hi, I would ask that the Germanium Transistor section be changed from:
The germanium transistor was more common in the 1950s and 1960s, and while it exhibits a lower "cut off" voltage, typically around 0.2 V, making it more suitable for some applications, it also has a greater tendency to exhibit thermal runaway.
to:
The germanium transistor was more common in the 1950s and 1960s, and while it exhibits a lower "turn on" voltage (Vbe), typically around 0.2 V, making it more sensitive, it also has a greater tendency to exhibit thermal runaway.  —Preceding unsigned comment added by 64.16.215.100 (talk) 21:26, 28 May 2010 (UTC)
thread_title:  Germanium Transistor Section 

message: In the equivalent circuit diagram for the Ebers-Moll model of a PNP transistor, aren't the two diodes shown facing the wrong direction?  Shouldn't the cathode of the diode (with the bar) be on the base (n-region) of the transistor?
76.120.125.115 (talk) 04:35, 18 August 2010 (UTC)
replies: text: Yes, I used an old version of the PNG. Sorry about that, fixed Inductiveload (talk) 12:39, 22 August 2010 (UTC)
thread_title:  Ebers-Moll model for a PNP transistor 

message: The article is accurate however it is impossible to understand unless you already understand how a transistor works. It would be benificial to refer out to the transistor wiki page which gives the required backgroud knowlage to fully understand this page—Preceding unsigned comment added by 195.33.114.129 (talk) 13:52, 10 February 2011 (UTC)
thread_title: complexity

message: I believe this article should not point to the "hybrid-pi model" article but include it into itself. It's the most important small-signal model. I don't see why the "h-parameter model" should be shown and the "hybrid-pi model" shouldn't. I rather prefer to see the opposite situation which is much more practical.
ICE77 (talk) 18:59, 21 April 2011 (UTC)
thread_title:  Hybrid-pi and h-parameter models 

message: In the graph of the operating characteristics, shouldn't the CE voltage be labeled with a "V" instead of a "U"?  This seems confusing.67.141.18.62 (talk) 02:26, 2 June 2012 (UTC)
thread_title: Graph

message: Please take a look at this page: http://www.markallen.com/teaching/ucsd/147a/lectures/lecture3/10.php
PNP arrow points to wrong direction!  — Preceding unsigned comment added by 65.44.170.169 (talk) 14:00, 28 June 2012 (UTC)
replies: text: In the page linked to by 65.44.170.169 and in the Wikipedia article the arrow for a PNP points toward the base, which is correct. A person drawing a schematic is free to position the arrow toward the top of the page, the bottom of the page, or either side, depending on how the circuit is connected. Jc3s5h (talk) 19:33, 28 June 2012 (UTC)
replies: text: Doesn't entirely aid clarity to draw one upside down though, does it. SpinningSpark 22:55, 28 June 2012 (UTC)
thread_title:  Schematic is wrong 

message: As someone else stated, there is an extreme amount of "technobabble" and yet very little information on common uses. As I recall from EE, there are at least two ways BJTs are commonly put to use... Let's see some simple circuits, maybe some biasing... emitter-follower vs. amplification... without going into all the molecular details.  — Preceding unsigned comment added by 71.197.246.206 (talk) 04:55, 6 July 2012 (UTC)
thread_title:  Theory vs application 

message: This inline comment (used twice) are better dealt with here (cut/paste): 
Where two of the three "Citation needed" tags are, was this comment: "I believe that Horowitz and Hill have a statement nearly identical to this; someone should verify that and replace this Fact with a ref to HH." Widefox (talk) 12:45, 28 July 2012 (UTC)
replies: text: Widefox's request makes no sense out of context. Please provide text we can search on to find the spot in the article. Jc3s5h (talk) 12:49, 28 July 2012 (UTC)
replies: text:  Clarified above. Here's a diff as well  Widefox (talk) 13:47, 28 July 2012 (UTC)
replies: text: I fixed the passage. Jc3s5h (talk) 21:53, 28 July 2012 (UTC)
thread_title: Outtakes

message: An NPN[clarification needed] transistor can be considered as two diodes with a shared anode.  Our proverbial bright 12-year-old reader is going to say "Hey, I can make a transistor with these two diodes I found" and when she wires it up and tries it, she's going to be disappointed.  This needs to be explained better - two back to back junctions, yes, but not just "diodes". --Wtshymanski (talk) 18:15, 1 August 2012 (UTC)
replies: text: I did some edits to make it more sensible.  Please comment or fix it better.  That mess was from an unnoticed IP addition of May 4, 2012.  Dicklyon (talk) 22:47, 1 August 2012 (UTC)
thread_title: Diodes

message: To clarify some confusion arising in recent edits, the operation of point-contact transistors requires minority carrier injection. SpinningSpark 21:11, 22 October 2012 (UTC)
thread_title:  Point contact transistors 

message: I've reconsidered the best way to bring this into the article.  I think it would be natural to first give the equations for collector current and base current as a function of voltage and then divide the former by the latter.  Both currents will have an exponential which will sort of divide out, leaving an equation that collector current is sort of proportional to base current with the proportionality is a function of collector current.Constant314 (talk) 16:14, 2 February 2013 (UTC)
thread_title:  Voltage Control, Current Control 

message: I have removed the following from the article;
My original intention was to move it the Early effect article since, without looking at it too carefully it seemed to belong there because it was inserted in the base-width modulation section.  However, on a second look it seems to be a derivation of Ebers-Moll.  However, without explanation (of at least the symbols used) it is perfectly useless in the article and is likely to discourage a large number of readers. SpinningSpark 09:03, 8 April 2013 (UTC)
thread_title:  Unreadable derivation 

message: I just removed the following from the article:
It was inserted at the start of the Ebers-Moll section, but does not seem to be relevant to Ebers-Moll (unless it was intended as a criticism of it).  This seems to be a resurrection of the voltage-controlled argument discussed ad nauseum above.  By all means lets have a voltage-controlled model in the article, but it needs to be properly explained in a section of its own, and it needs to be properly cited to a reliable source. SpinningSpark 10:50, 22 June 2013 (UTC)
thread_title:  Voltage controlled model redux 

message: I've just created hfe as a redirect to Bipolar_junction_transistor#h-parameter_model. It's the best link target I could see to hand, but we have a pretty obvious need for an entry-level article on hfe. Anyone fancy writing a decent explanation? Andy Dingley (talk) 11:18, 24 November 2013 (UTC)
thread_title:  h<sub>fe</sub> 

message: I thought I'd leave a few lines in the talk page since my edit in the previous version 'introduced misleading language, and if misleading bits were clarified, the lead would become as long as the whole article'.
*"By design, most of the BJT collector current is due to the flow of charges injected from a high-concentration emitter into the base where there are minority carriers that diffuse toward the collector..."
::Injected charges are (i.e. become) the minority charge carriers in the base. It is not like "well, charges are injected from emitter to base, and then there are also minority charge carriers in the base region and they diffuse toward collector". There are indeed thermally generated electron-hole pairs in the depletion region (which are majorly recombined after generation, and the small remaining portion leads to a reverse current) but this sentence is (should be) talking about injected charge carriers. Also, as a digression, misleading language is much better than misleading information I think; it's statistics (probably not Boltzmann though).
*"By design..."
::What's special about BJT design is not that collector current is due to flow of charges from emitter to collector. What's special about BJT design is that;
Three layers are properly doped (i.e. Nemitter > Nbase ~ Ncollector) so that diffusion from emitter will be an optimally effective mechanism in the conduction.
  Base layer is kept relatively narrow so that the heavily doped emitter region causes the emitter-base junction to span over almost all of the base region leaving very little neutral (doped) region for annihilation of charge carriers as a result of electron-hole recombination. So, by design, a relatively small current compared to that of emitter's and collector's goes through base (like walking on water).
::Here is what happens in active mode (in which BJT is used for amplification purposes rather than switching) step by step:
:#Forward biased emitter-base junction contracts (compared to equilibrium width). Since emitter is heavily doped compared to base, most of the width of emitter-base junction still lies on the base side.
:#Majority charge carriers of emitter region are injected into base region where they are minority charge carriers (rather than majority charge carriers).
:#Since base region is relatively narrow (and therefore, width of the neutral region outside the depletion zone is relatively narrow as well), and since majority charge carrier concentration in base is relatively small, diffusion rate is much larger than recombination (~annihilation) rate. Therefore, most of the emitter current is swept through base-collector junction.
:#Reverse biased base-collector junction expands (compared to equilibrium width). This means the electric field within the depletion region remains, and indeed gets stronger, in the direction of flow, not against it. Therefore, charge carriers in the base-emitter region drift through neutral region in collector. And finally, from the neutral region of collector, they continue toward the attractive terminal of the voltage source.
::Apart from the particular design details given above, the law of the junction explains how the above design is used for amplification purposes:
:: c_{biased} = c_{equilibrium} ~ \text{exp} \left ( \frac{eV}{kT} \right )
::,where cbiased and cequilibrium are biased and equilibrium concentrations of minority charge carriers at the end of depletion zone in the region to which carriers are injected, e is elementary charge, V is applied voltage, k is Boltzmann constant, and T is absolute temperature. Note that a higher cbiased implies a higher BJT collector current.
::Since any change in emitter-base voltage changes the diffusion through base region (and thus in collector current) exponentially, a BJT can be used for amplification purposes.
*'Since the central fundamental concept in BJTs' working is minority carrier injection, these devices are classified as minority-carrier devices.'
::I think it is important to mention the widely referred working principle (minority carrier injection) of any semiconductor device whose operation relies on carrier motion through junctions.
* A note about the terms anode and cathode
::Electrical engineers (and Wikipedia) define the anode, for all circuit elements (including batteries), as the terminal to which positive (conventional) flow enters, or equivalently, the terminal from which the negative (electron) flow departs. This definition is intuitive for batteries: Anode of a battery is where the oxidation reaction occurs, which produces electrons and therefore makes the terminal negatively charged, and thus a battery’s anode is where the positive (conventional) flow enters. However, when the term anode is used for other polarized circuit elements such as diodes, the connection of these elements to a battery circuit becomes non-intuitive: anode of the diode is connected to cathode of the battery, and cathode of the diode is connected to anode of the battery (just like connecting two batteries in series; anode to cathode, and cathode to anode). Also note that, in order for a diode to conduct electricity, the p-type semiconductor end must be connected to the positive terminal of the battery, and the n-type end must be connected to the negative terminal of the battery, so that holes and electrons are repelled by the terminals and can overcome the electric field in the depletion region. Therefore, according to definition of the term anode, p-type end of a diode is called anode. However, majority charge carriers in the p-type end of a diode are positive charged (i.e. hole), and calling it anode is non-intuitive.
::Due to these inconsistencies, it is better to avoid using terms “anode” and “cathode” unless the discussion is confined to electrochemistry (e.g. batteries), and in general it is always better to refer to terminals of a diode as p-type and n-type terminals, and terminals of a battery as positive and negative terminals.
*Apparently there has been a demand for simplification since 2012: "This section may be too technical for most readers to understand. Please help improve this section to make it understandable to non-experts, without removing the technical details. The talk page may contain suggestions. (July 2012)".
::Anybody who possess the power of non-misleading language and think that it would improve the article is welcome to incorporate any part of this message, as-is or modified, to the article.
*"...if misleading bits were clarified, the lead would become as long as the whole article."
::This is interesting.
85.110.21.35 (talk) 19:29, 9 April 2014 (UTC)
replies: text:  "[2]" at the end of the section name is a link created with Template:Diff2. Not everybody who use wikipedia knows how to use it, but everybody who use wikipedia knows how to follow links. 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)
replies: text: The statement you've just quoted above was there before I edited, after I edited, and after my edit was 'restored'. It is still there. It's hard to make sense out of your language (I am not saying it is misleading). 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)
replies: text: Rather than wasting our and probably others' time, I'd trust your wisdom (in wikipedia). good day/night. 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)
thread_title:  Missleading language in the previous phrasing {{Diff2|603450607}} 

message: When you link to Bipolar junction transistor#Ebers–Moll model, the article actually has two places with the same identifier to jump to. It means the generated HTML page is technically invalid; see the second point under Template:Anchor#Limitations, or tools:~dispenser/cgi-bin/rdcheck.py/Bipolar junction transistor for instance. There is no difference in the dash used (an en dash) between the heading itself and the second Anchor argument. Perhaps my original edit summary wasn’t clear enough, but I hope this clarifies things and you are able to remove the problem anchor again.  Vadmium (talk, contribs) 01:46, 29 July 2014 (UTC)
replies: text: I always thought that anchors could be used to protect against heading name changes, but apparently not. SpinningSpark 07:59, 29 July 2014 (UTC)
thread_title:  Anchor duplicates Ebers–Moll heading 

message: I have issues with these images. 
:# This image of the PNP BJT schematic symbol:   is not wrong but inconsistent with canonical practice when introducing schematic symbols, which is to show transistor symbols rotated to have the emitter or source terminal at the bottom. The NPN symbol is shown properly in this way. The article on "Electronic Symbols" uses this same inverted PNP symbol. Showing an rotated forms of symbols should be done in that article, if it deemed relevant at all. 
:# This image of the "NPN BJT with forward-biased E–B junction and reverse-biased B–C junction":    is very confusing, and I think, wrong. It shows both conventional (black arrows) and physical (internal) current flows. See "Electric Current: Conventions""[]". Normally only one flow model is applied in explanations. If we are explaining how to design electronic circuits, we use "conventional current flow" (current flows from positive to minus potentials). But explaining the actual physics, as the Diode article does, we should use actual physics and "physical current flow". Since the purpose of this image is to reveal the internal operations of the transistor, we should use only physical current flow throughout. 
:# Other images ("Structure and use of NPN transistor", "Structure and use of PNP transistor", Ebers-Moll models, and subsequent images) show Conventional current flow (black arrows). As explained above, this only applies to design of electronic circuits. So if the purpose of these parts of the article is to how to use the transistors (i.e. design and model circuits) then conventional current flow is correct, but the switch from one to another within the article should be very clearly explained. Or, perhaps a better choice, move these parts to a new article on "designing with transistors" (The topic of current flow direction is a well-known source of confusion in electronics.). 
Rich S 10001 (talk) 15:27, 7 September 2014 (UTC)
thread_title:  Images used here are Inconsistent 

message: The value of this gain for DC signals is referred to as h_{\text{FE}}, and the value of this gain for AC signals is referred to as h_{\text{fe}}. However, when there is no particular frequency range of interest, the symbol \beta is used[citation needed].
There are different versions between the PNP and NPN active mode descriptions, with one [citation needed] and the other with a citation. It seems to me that β is used in a less formal context, and Hfe when one needs to more exact. One might indicate, in general, the gain of an amplifier without a frequency response graph might be β, but with a graph Hfe, or β without a specific bias, but Hfe once the bias is specified. But is there a reference that explains this detail? Gah4 (talk) 07:16, 26 April 2015 (UTC)
replies: text: hfe arises from the h-parameters and thus has implied test conditions (short-circuit output) from the definition of h-parameters.  The test conditions for beta, on the other hand, must be explicitly stated.  Thus, beta can be specified for more realistic operational conditions.  The hfe can be thought of as a specific instance of beta under the given test condition.  The difference has nothing to do with frequency range.  Beta can be specified for DC and small-signal just as well as it can be for hFE/hfe although there is no generally recognised separate symbols for beta for these two cases as far as I know.  Most text books simply treat hfe and beta as synonyms. SpinningSpark 12:55, 26 April 2015 (UTC)
thread_title:  Beta vs Hfe 

message: I see this equation under the DC section for the collector current:
: i_{\text{C}} = I_{\text{S}} \, e^{\frac{v_{\text{BE}}}{V_{\text{T}}}} \left(1 + \frac{V_{\text{CE}}}{V_{\text{A}}}\right)
Should the equation be like this instead since it's under the DC section?
: I_{\text{C}} = I_{\text{S}} \, e^{\frac{V_{\text{BE}}}{V_{\text{T}}}} \left(1 + \frac{V_{\text{CE}}}{V_{\text{A}}}\right)
If it should not be then it contradicts these two equations under the Ebers-Moll model:
: I_{\text{E}} = I_{\text{ES}} \left(e^{\frac{V_{\text{BE}}}{V_{\text{T}}}} - 1\right)
: I_{\text{C}} = \alpha_F I_{\text{E}}
ICE77 (talk) 19:54, 14 October 2015 (UTC)
thread_title:  Collector current equations 

message: Although this Wikipedia article has some good explanations and illustrations some parts are very technical and way beyond the comprehension of the non expert. That aside though, I suggest that the introduction could be rationalised and better structured to give a more general, simpler, more readable, and more easily understood introduction to the BJT. CPES (talk) 05:49, 19 October 2015 (UTC)
thread_title: Introduction

message: This article had 'on the order of' which I changed to 'in the order of', thinking the original was just a simple error. Here in the UK, I had never come across the 'on' version. Subsequently Glrx reverted it back to 'on' so it was no error. Intrigued, I did a bit of investigating and it turns out there are three versions: 'on the order of', 'in the order of', 'of the order of'. 'on' is used more in the US, while 'in' is common in the UK, but the strictly correct wording as far as I can tell is 'of the order of'. http://english.stackexchange.com/questions/94451/something-is-of-in-the-order-of
That's the great thing about Wikipedia, you always learn something new. CPES (talk) 10:44, 26 October 2015 (UTC)
replies: text: Prepositions are screwy. If you want some fun, choose a random verb and then follow it with a prepostion: pull off, pull out, pull through, pull at, pull behind, ...; tie up, tie down, tie on, .... Glrx (talk) 16:31, 26 October 2015 (UTC)
replies: text: This is less preposition than idiom IMO. Local usage can & does vary a lot, like this case. It can, in some cases, completely change the meaning: in the U.S. & Canada, you'd root for a sport team; in Oz, "root" is slang for sex...  TREKphiler any time you're ready, Uhura 21:10, 26 October 2015 (UTC)
thread_title: on/in/of the order of

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thread_title:  External links modified 

message: User:Gah4 justifies this edit with the edit summary
The passage in question, before it was changed by an IP editor, stated
User:Gah4 wants to retain the version by the IP editor, which changes the last occurence of "base" to "emitter". But the sentence says the transistor is active. This is ordinarily taken to mean the active region, which is different from the saturation region, which User:Gah4 mentions in the edit summary. Jc3s5h (talk) 04:06, 6 December 2016 (UTC)
replies: text: I can't see how it would be correct either way.  Why not get a better definition from a source?  As for saturation, it is unfortunately defined in roughly opposite ways in bipolar and MOS devices.   In bipolar NPN, base > collector would be saturation region (roughly); while emitter > collector would mean that emitter and collector have been interchanged; not a region.  Dicklyon (talk) 04:26, 6 December 2016 (UTC)

text: This book says base < collector in active region; opposite of what our article has been saying, and I agree (though it can go slightly the other way and still be active). Dicklyon (talk) 04:33, 6 December 2016 (UTC)

text: I think the problem was just that voltage differences were being described in an unconventional direction, and that with that fixed, Gah4's change makes a lot more sense. See if you agree. Dicklyon (talk) 04:49, 6 December 2016 (UTC)

text: Generally, I'm pretty sure "potential difference measured from A to B" usually is taken to mean V_A - V_B.  But is was the other way around here.  If there are sources that do it that way, show me. Dicklyon (talk) 05:03, 6 December 2016 (UTC)
replies: text: OK, first we are talking common emitter configuration. Next, the voltages will all be the other way for PNP vs. NPN, but Vbe and Vce are normally the same sign for active region.  There are many definitions here: https://www.quora.com/What-is-saturation-active-region-in-a-transistor but it looks to like any collector current less than saturation is active.  At almost, but not quite saturation, such as Schottky TTL, Vce should still be less than Vbe, but not quite as much. But otherwise, the usual descriptions of common emitter mode are in terms of Vbe and Vce. Gah4 (talk) 06:29, 6 December 2016 (UTC)
thread_title: Active vs. saturation region

message: Why does this article NOT have a "complementary pair" section?  It needs to be added.  • Sbmeirow • Talk • 04:53, 26 March 2017 (UTC)
thread_title:  Complementary Pairs 

message: I'm trying to follow this sentence (and I DO have an understanding of BJTs). It seems to me it should end with " ... so the current-control view is often preferred." (BUT PLEASE READ MY WHOLE COMMENT)
"The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modeled as a transconductance, as in the Ebers–Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred."
Even just syntactically/semantically, the sentence starts with discussing the voltage-control model, then has a "but," so it would make sense that the remainder talks about the alternative, the current-controlled model. I suspect whoever wrote this knew what they were trying to say, but accidentally wrote voltage instead of current near the end of the sentence.
But then again, if there's a resistor in series with the base, and this resistor is dropping (say) several volts, then the voltage between the (non-base side of the) resistor and the emitter IS approximately linear to the collector current, and this is a "mostly linear" transconductance. Maybe THAT is what the writer meant, but either way, it's not clear.
On the third hand (and I'm starting to think this is the "real" explanation), the reference to differential amplifiers implies (but does not state!) very low signal levels across Vbe (a few millivolts or less), and such signals ride on a small and "mostly linear" portion of the exponential curve (where, for larger signals, the collector current doubles with approximately every 20mV increase in Vbe), and THIS could be what is meant. Even here it should say a linearized voltage-control view, rather than just voltage-controlled view.
I find the sentence confusing, apparently because it is missing some qualifying information, but rather than just adding such info I hope it would be rewritten for clarity. I've never had to think through a sentence so hard even though it might be technically correct.Benbradley (talk) 05:37, 12 December 2018 (UTC)
replies: text: The sentence should end with voltage control.  The control voltage is applied directly to the base in a common emitter configuration.  The output is the collector current.  The "it" that is linearized is the exponential input voltage to collector current curve.Constant314 (talk) 06:10, 12 December 2018 (UTC)
replies: text: I think that in a common-emitter configuration the current-control view would be preferred, since it's linear instead of exponential.  But in the differential transconductance amplifier, the voltage-control view is preferred, since the behavior is close enough to linear for small voltage differences (and for larger differences you can a tanh compression, approximately at least). Dicklyon (talk) 06:26, 12 December 2018 (UTC)
replies: text: Current control is linear-ish, with an unpredictable departure from linearity that varies noticeably from device to device.  Voltage control is strongly non-linear with a very predictable  curve that is strongly matched from device to device.  In the diff amp, device matching is far more important than linearity.  With regard to the common emitter stage, in my own work, it depends on the nature of the source that is driving the stage.  If the driver is high impedance , then I use current control.  If it is low impedance, I use voltage control.  At high frequency, due to the Miller capacitance, common emitter stages have a low output impedance and hence look like voltage sources.  So, a first CE stage is ready to drive a second CE stage with voltage control of the second stage.Constant314 (talk) 19:20, 12 December 2018 (UTC)

text: I think the sentence is referring to a small-signal analysis, where all nonlinearities are appproximated as linear. In a small-signal analysis a voltage control model would not have the difficulties it would have in a large signal analysis. Jc3s5h (talk) 12:36, 12 December 2018 (UTC)
thread_title:  Should this sentence end with voltage-control, or current-control? 

message: The article indicates that reverse active mode is seldom used.  In most types of circuits, I expect that is true, but it is an important part of the operation of TTL circuits.  Specifically, the advantage of TTL over DTL. As TTL is getting less common, and CMOS more, I suppose it is less common than it used to be, but still not so seldom. Gah4 (talk) 07:54, 29 March 2020 (UTC)
thread_title:  reverse active mode 

message: This formula in the Ebers Moll model section comes out of nowhere. J_n(\text{base}) doesn't appear in any formula and nothing explains what base internal current is. I can't fix it because I do not know.
J_{n\,(\text{base})} = \frac{1}{W} q D_n n_{bo} e^{\frac{V_\text{EB}}{V_\text{T}}}
2600:8807:5480:713:EC68:B0E5:991B:BFAC (talk) 00:05, 25 May 2020 (UTC)
thread_title:  Why is there a random formula for <math>J_n(\text{base})</math> 

message: The "Technical" tag on this section of the BJT article does not seem to apply any longer; for example, many inline citations now exist, leading directly to Wikipedia articles that explain the concepts involved. I have read the section and do not see the need for this tag at this date; also, the Talk page does not contain much discussion of this issue, and certainly nothing that can be decribed as "active".
As the BJT is a complex system, there will be a need to use technical terminology in explaining it. This is no different from any other advanced/non-introductory concept and does not (in my opinion) warrant a tag "in-and-of itself". I do believe a few tweaks/improvements can still be made (and am happy to make them), however I believe the "Technical" tag has served its purpose in the last decade and is no longer needed.
I am raising the issue here to see if anyone has strong feelings about this, and also if anyone is willing to help with improvements. Snooze Dogg (talk) 12:34, 27 July 2022 (UTC)
replies: text: Removing the tag is much easier than fixing the article. But have we really done all we can to make the presentation more accessible, or is it infested with relativistic effects, excess math typesetting, and spurious ISO standards? --Wtshymanski (talk) 02:20, 14 August 2022 (UTC)
replies: text: I vote for removing it. Removing it doesn't say that the article is perfect, as no article ever is. With , we usually know we can remove it when we supply a (hopefully good enough) citation. In this case, the line is fuzzier. There is no completely untechnical explanation of a bipolar transistor. (There might almost be for a MOSFET.) If the article is within the range of the usual article on a technical subject, I think we can remove it. Gah4 (talk) 12:14, 15 August 2022 (UTC)
thread_title:  Propose removal of "Technical" tag (on section "Function") dating from 2012