Talk:Bipolar junction transistor

Polarity of germanium transistors

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

external reference bjt_models.pdf gone

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)

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)

Ambiguity and repetition

The sentence "This gain is usually 100 or more, but most robust designs only depend on it being very large" is ambiguous. It just doesn't make much sense and should be reorganized.

Section 5.1.1 Ebers–Moll model is redundant with Section 1.2 Transistor 'alpha' and 'beta'. The same concepts and the same equations are presented. One of the two sections should be merged into the other one. I would myself merge 1.2 into 5.1.1.

ICE77 (talk) 05:49, 19 April 2009 (UTC)

Yeah, not great. I worked on it some. I notice the Ebers–Moll section had this emitter efficiency thing disconnected from anything else since this edit back in 2006; I took it out; but there remains an undefined symbol in the base current density formula that might be related; find a source and work on it? Dicklyon (talk) 06:34, 19 April 2009 (UTC)

The sentence "This gain is usually 100 ..." is repeated twice. You fixed the first occurrence but not the second.

I don't know what you are referring to with "emitter efficiency thing disconnected" and "undefined symbol in the base current density formula". Be more explicit so I can see what you are talking about.

ICE77 (talk) 00:36, 4 May 2009 (UTC)

I had removed this bit: "Emitter Efficiency, $\eta = \frac{J_n(\text{base})}{J_{\text{E}}}$, is the ratio of current injected into the base to the current in the emitter; the two differ due to backward injection from the base into the emitter and to recombination. See carrier generation and recombination." as it didn't connect to anything, as far as I could tell.

There's still a n_bo in the formula, and I don't know what it is; the section doesn't say; I haven't tried consulting sources yet. Maybe this n was supposed to be the eta thing that I had removed? Dicklyon (talk) 05:39, 4 May 2009 (UTC)

η is just a ratio of currents. n_bo most likely refers to the concentration of electrons (n) in the base (b) of an NPN transistor at equililbrium (o) since electrons are minority carriers in the base of an NPN transistor and they are responsible for current in the device.

ICE77 (talk) 23:46, 5 May 2009 (UTC)

Plausible guesses, but neither was connected to anything else in the section, so what we really need is a source; so far I don't see these symbols or anything like them in sources. nbo does look like a carrier density, since it multiplies q. Dicklyon (talk) 04:19, 6 May 2009 (UTC)

Concentration of electrons or holes and electron charge can coexist within a current equation. I have taken notes from a semiconductor book where q and n or q and p are multiplied to obtain a current. q is just a constant. An example of an equation where this is true is the equation for resistivity.

ICE77 (talk) 23:45, 6 May 2009 (UTC)

A simple model of the transistor consisting of an LED and a photodiode

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/β_F) 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 (β_F) 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)

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)

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)

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)

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)

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)

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)

The purpose of a model is simplicity, not accuracy. just-emery (talk) 15:15, 26 May 2009 (UTC)

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)

Minority carrier device

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)

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)

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)

Active-mode PNP transistors in circuits figure incorrect

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)

The $6 Man

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)

Germanium Transistor Section

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)

Ebers-Moll model for a PNP transistor

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)

Yes, I used an old version of the PNG. Sorry about that, fixed Inductiveload (talk) 12:39, 22 August 2010 (UTC)

Ebers-Moll model for NPN transistor

In the Ebers–Moll Model for an NPN transistor I think that α_R I_ED should be α_R I_CD. Further α_F I_CD should be α_F I_ED. —Preceding unsigned comment added by 78.33.14.67 (talk) 08:53, 29 October 2010 (UTC)

Based on my recollection and page 328 of Ben Streetman's Solid State Electronic Devices (1972) I agree with 78.33.14.67. Jc3s5h (talk) 12:40, 29 October 2010 (UTC)

complexity

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)

Hybrid-pi and h-parameter models

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)