Which is currently being taught; electron flow or conventional flow? - Page 1
Forum section: electronics / general

author: W9GFO
author_rank: Regular Contributor
timestamp: December 29, 2019, 09:38:09 pm
content: When discussing something like how current travels through a transistor do professors and/or people in the industry describe the behavior in terms of electron flow or in conventional flow? I know that the difference between electron flow and conventional flow is taught, but if the flow type is not specified how do you know which is being used?I came across some course material that described the operation of an NPN transistor in the same way that I would expect a PNP transistor to be described - I thought that it was an error, however it was intentional. Depending upon which flow the describing person is using, either could be correct. If the type of flow is not specified, which is the correct one to use?

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: December 29, 2019, 09:54:47 pm
content: I expect to see conventional at the level of engineering. The boundary generally lies somewhere in the domain of physics. Conventional current is a useful andconsistentabstraction; for instance, it cleanly bundles together all charge carriers, including protons, electronholes, etc.Of course, the difference absolutely needs to be taught.

author: IanB
author_rank: Super Contributor
timestamp: December 29, 2019, 10:21:24 pm
content: Quote from: W9GFO on December 29, 2019, 09:38:09 pmIt depends on the context. If studying engineering at professional level (bachelors, masters or above) then the question will not be important and will not be worthy of discussion. Quite simply voltage has increasing positive potential when measured from more positive to less positive, and current has a tendency to flow with a positive sign from points with a more positive potential to points with a less positive potential. All equations and calculations will be based on this standard convention.The idea of electron flow or conventional flow may be taught in elementary classes in high school to give students a grounding in atomic theory, but once introduced it will soon be left behind.Semiconductor physicists of course are in different world and know exactly what they are doing, but their work is in a specialized domain and is not relevant to general education.

author: IanB
author_rank: Super Contributor
timestamp: December 29, 2019, 10:25:34 pm
content: Quote from: W9GFO on December 29, 2019, 09:38:09 pmThat image you posted seems incorrect. An NPN transistor will be biased towards the on state when a positive voltage appears at the base relative to the emitter and consequently a positive current will flow into the transistor at the base.It is best to ignore such materials as that one that seem written to confuse people.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 30, 2019, 03:42:01 am
content: Does the Navy still do electron flow? Even if not, you'll likely find plenty of old material from when they did.It doesn't actually matter, as long as it's consistent.Tim

author: KL27x
author_rank: Super Contributor
timestamp: December 30, 2019, 05:42:52 am
content: If this is a vote, I'd say the descriptions in your upload/link are whack. Conventional current should be understood as the defacto, unless otherwise specified. And in this case it has not been otherwise specified.Doesn't matter which way the electrons go. The current is positive to negative, by convention. They could specify by saying electron flow rather than current.

author: magic
author_rank: Super Contributor
timestamp: December 30, 2019, 03:18:24 pm
content: Quote from: KL27x on December 30, 2019, 05:42:52 amAnd they would still be wrong because half of the time it's the holes that make all the differenceTeaching this electron current convention and pretending that it's the norm is totallyat this point.Why is the arrow pointing outwards if you say it's a small current flowing from E to B, huh?

author: ocw
author_rank: Regular Contributor
timestamp: December 30, 2019, 03:56:10 pm
content: Electronics 101: Electronic current flow is from positive to negative since this is what the first people working with electronics (do not say 'incorrectly") speculated. In tubes, the filament attracts "positrons" being emitted from the plate.Electronics 301: We lied to you in Electronics 101 about electric current, forget everything which we taught you, here is what is actually true...Continuing a lie because it was once thought true (the earth is flat) does not make sense. Long ago, in my early teens, I could handle electron flow, holes (a missing electron moving, not protrons), etc. from the beginning of my electronic education.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 30, 2019, 04:29:08 pm
content: Why are Native Americans still called "Indians"?

author: German_EE
author_rank: Super Contributor
timestamp: December 30, 2019, 05:39:29 pm
content: For as long as I can remember I have been taught that in an NPN transistor current enters the base and collector and flows out of the emitter. This implies that current flow is positive to negative.However, the cathode in a vacuum tube emits electrons which then flow through the grid)s) to the anode, meaning that in a vacuum tube circuit the flow is from negative to positive.I shall therefore carry on working with transistors.

author: james_s
author_rank: Super Contributor
timestamp: December 30, 2019, 06:05:58 pm
content: There's a reason it's called "conventional flow".Every EE knows that electrons actually flow from negative to positive but in most cases conventional flow is used because it's the convention. When you are designing or analyzing a circuit it doesn't matter which way the electrons are flowing since you can't see them anyway. Pretend they are flowing from positive to negative because that's how all of the schematic symbols are defined. If you're working with vacuum tubes it may be helpful to think in terms of electron flow but how many people are doing that anymore? Those that are already know.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 30, 2019, 06:08:40 pm
content: Quote from: james_s on December 30, 2019, 06:05:58 pmFully agree.The rest is just wank.(Of course the basics still need to be known, but as you said, that doesn't serve any purpose when analyzing a circuit.)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 30, 2019, 07:18:12 pm
content: Some day I want to do some glassblowing and make a proton tube. I don't think much of a "space charge" can be made (we must start with neutral dihydrogen, so on the order of >13.6eV is required to do anything; the resulting "virtual anode" will be about as hot), which will greatly limit available current (and perveance), but other than that, the transconductance and transit time should be perceptibly, and proportionally, worsened (i.e., by ~2000x). Transit time is typically a few ns for electron types, so at some µs, it will be obvious on the oscilloscope.Tim

author: bson
author_rank: Unknown
timestamp: December 31, 2019, 06:48:42 pm
content: Quote from: james_s on December 30, 2019, 06:05:58 pmWell, like pretty much every other EE I was taught somewhere around day 1 that I = Q/t. Hence, positive current is a positivecharge flow. Because electrons are negatively charged they flow in a direction opposite to the current. Signs matter.

author: bob91343
author_rank: Super Contributor
timestamp: December 31, 2019, 07:12:16 pm
content: A 'hole' is a missing electron. If a hole flows, it will be in the conventional, or positive direction. However, a hole isn't something tangible - it's something missing. In order for a hole to move, an electron has to fill the hole from somewhere else, and thus it's still electron flow. After all, a vacuum cleaner doesn't suck, it simply moves air in such a way as to cause atmospheric pressure to move air in a desired direction.Having said all that, as an engineer I have always used conventional current. I had to change, as my college classes required it. It's never caused a problem, and I automatically think in terms of conventional current. That allows me to analyze and design with PNP or NPN for instance.About the only time it feels right to work with electron flow is when analyzing the inner workings of a vacuum tube. Which way does current flow in a voltage regulator tube or a neon bulb?

author: MT
author_rank: Super Contributor
timestamp: December 31, 2019, 07:23:27 pm
content: 1:Why was schematics drawn the conventional way and not the unconventional way whos the right way?2:Why do American Indians get angry when labelled Native Americans? despite Vikings saw them before Christopher Columbus!?3:Why is electrons described as ball to fill a hole when physics describe electrons to be everywhere and nowhere orbiting around the nucleus?

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 31, 2019, 08:10:26 pm
content: Quote from: MT on December 31, 2019, 07:23:27 pmThings are going to get interesting with the rise of (actual) Indians in the US. How would you describe their children? They're genetically Indians, but they're born in the US.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 01, 2020, 01:29:45 am
content: Quote from: NiHaoMike on December 31, 2019, 08:10:26 pmWouldn't they just be "Americans"?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 01, 2020, 01:49:50 am
content: If you ask them what they prefer to be called, they'll say "Indians".Tim

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 01, 2020, 02:31:19 am
content: Interesting. But perhaps it is Australia that is the odd one out, since official documents here don't ask about race ... at most it's country of birth.(The one exception to this policy is Aborigines and Torres Strait Islanders, who make up about 3% of the population. The census, university applications, etc.dospecifically ask about these two ethnicities. Members of these groups seem much more likely to identify as such, though that doesn't mean there's any causal relationship, as the situation is roughly as complex as that of Native Americans in the US.)

author: EEVblog
author_rank: Unknown
timestamp: January 01, 2020, 03:21:51 am
content: This thread had better stay on topic...

author: vk6zgo
author_rank: Super Contributor
timestamp: January 01, 2020, 09:43:46 am
content: Quote from: magic on December 30, 2019, 03:18:24 pm"Holes" are a useful fiction describing the supposed flow of the place where an electron formerly was----in the opposite direction to the direction in which the displaced electron travels.It is not usual to refer to "holes" when describing current flow in conductors.The "arrow" points outwards because it follows the convention set up in the early days of electronics, which used "Conventional Current Flow".The convention for drawing CCF is with the arrow point pointing away from the more positive side of the circuit, & towards the more negative side.How does a vacuum tube work, using CCF, huh?

author: sibeen
author_rank: Frequent Contributor
timestamp: January 01, 2020, 10:24:48 am
content: Quote from: T3sl4co1l on December 30, 2019, 03:42:01 amBelow is the response I gave in a recent thread about sign. It's not just the US navy that goes down this route, I started in electronics in the Oz army. :I had to think about this and grinned to myself when reading this as I suspect that I change which way I define the direction depending upon which day of the week it is. This may be a result of my electrical education. I started out with a four year apprenticeship as an electronics tech in the late 70s. The interesting tidbit is that military techs, at least in the English speaking portion of the world, get taught electron flow. I've never been able to track down the why of that and it's always interested me as to why that occurred. A few years later I decided to go down the university route and was taught thecorrectconventional current flow.Still to this day when I'm looking at a circuit I'll revert to electron flow and this occasionally causes consternation with people I'm showing the workings to as "I'm doing it wrong" only to be a tad bemused when my answer turns out to be the correct one.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 01, 2020, 03:17:45 pm
content: Quote from: sibeen on January 01, 2020, 10:24:48 amThe whole point of "conventional" is to make things understandable and unambiguous to all. I'm not sure what kind of fun you'd find in not following the most usual convention just to feel "correct" (whereas, as some have explained above, correct here is just another convention anyway, but as the above sentence shows - it was consterning people - a much less common convention in this particular context).Probably gives some a feeling of superiority. Oh well. As long as the design and analysis is correct, who cares? Have you actually seen an electron yet?Oh, but one common situation where conventions can still be mixed up is with some electronic symbols such as transistors. MOS transistors, for instance, are usually represented with the arrow in the opposite direction depending - usually - on whether the symbol is meant as a "raw" transistor (on microelectronics schematics for instance) or as a discrete one...

author: German_EE
author_rank: Super Contributor
timestamp: January 01, 2020, 03:39:01 pm
content: In a similar vein there is something that I need help withAn NPN transistor is used in a negative ground circuit and the transistor symbol has the arrow pointing AWAY from the deviceAN N-Channel MOSFET is used in a negative ground circuit and the MOSFET symbol has the arrow pointing TOWARDS the device.Please could someone explain what is going on here?

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 01, 2020, 03:59:12 pm
content: Thanks to random historical agreements and npn. At this era the rail at top of diagram is positive, ground is zero and arrows on schematics are more or less readable. Or else the schematology would be unlearnable.What is still confusing are small things, which one can stop noticing after a while. For example the symbol for battery has positive plate drawn smaller than negative. Other annoyance is arrow direction on current source symbol. This current source (I can not even remember it correctly for longer than a minute) is worst.Edit: However not everything is safe to talk about, because if aliens with all reasonable choices of polarities and flows will meet us, the shameful state of our science may cause an enragement and intergalactic war.

author: newbrain
author_rank: Super Contributor
timestamp: January 01, 2020, 04:12:10 pm
content: Quote from: German_EE on January 01, 2020, 03:39:01 pmFirst of all, negative or positive grounds have nothing whatsoever to to do with it.I'm sure you know you can use PNP BJTs and P-channel MOSFETs in a circuit with a "negative" ground - after all, ground is just the place you pick and say "this is my 0 V reference".N-channel MOSFETs have a p doped semiconductor for substrate, and that explains the arrow pointing in, as for a PNP BJT.As the the p substrate will form a PN diode with the Drain (and possibly the Source if it's a separate terminal), the arrows gives you the right indication!EtA: I really don't get all the fuss.What's so complicated in understanding thatas definedcurrent goes from higher potential to lower potential. Since the current carriers aremost of the timeelectrons, and they have a negative charge, they go the opposite way.My description of how a triode works is not going to change for this.

author: madires
author_rank: Super Contributor
timestamp: January 01, 2020, 04:45:48 pm
content: Quote from: W9GFO on December 29, 2019, 09:38:09 pmIf not specified or not obvious from the context we assume the conventional flow (another convention).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 01, 2020, 05:33:36 pm
content: Quote from: German_EE on January 01, 2020, 03:39:01 pmThe arrow shows the direction of minority charge carriers, technically speaking. Practically, that means there's a P-N diode junction there.The BJT is a trans-diode, with the B-E side being the primary (controlling) diode, and C-B (no arrow, though early (dual whisker) types were often drawn that way) being controlled consequentially.The MOSFET acts in parallel with a (body/substrate) diode. The gate biases a surface layer into conduction, bypassing the diode; the layer carries a current regardless of polarity -- hence why synchronous rectification works. Because there are effectively two paths in reverse, there's a junction dot in the symbol, showing one current path through the substrate diode (which is normally reverse biased in switching and amplifier service) and one through the channel (which is conditionally conductive).Such a superficial explanation does of course miss how BJTs can saturate at low or negative voltages, which they actually do, much like FETs; but it fits naturally with Darlington and IGBT types, which do not saturate all the way to zero.So now that you know this, whenever you see the shorthand MOSFET symbol,your eyes may see: "wait, that's a diode shorting from top to bottom!" Well, yeah, without mincing words: it's a retarded symbol. What theymeantwas a regular NMOS I guess drawn in the style of an NPN, but what they got was something entirely different.Ironically, this is a fine way to draw an IGBT, though with angled C/E lines; that is, as a BJT with insulated gate instead of base wire.Also incidentally, the MOS IC shorthand omits the arrow, and denotes channel type by omitting or placing a circle on the gate (to suggest negation for the P-ch). This is perfectly fine, and consistent with IC design (where you do in fact have independent, and usually symmetric, D and S connections, and a common substrate to VDD/VSS that can be assumed when not indicated otherwise).Tim

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 01, 2020, 06:38:33 pm
content: Quote from: T3sl4co1l on January 01, 2020, 05:33:36 pmYes, much better! Unfortunately, the above symbols I mentioned and you showed are still frequently used in microelectronics courses and schematics...

author: SparkyFX
author_rank: Frequent Contributor
timestamp: January 01, 2020, 10:01:02 pm
content: Over here the nomenclature taught is "technical" and "physical" direction. As all schematic symbols use the technical direction (and make more sense applying them), it is hard to come up with an example in which it actually matters as long as all schematic symbols are drawn following the methodology. It only breaks the system when someone tries to mix both.But anyway, i like the approach of seeing an electron as a negative charge moving in a certain direction.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 02, 2020, 04:11:02 am
content: Quote from: W9GFO on December 29, 2019, 09:38:09 pmGoing back to this original posting, the vital clue is in the transistors pictured.They date from an earlier period, as does the information shown with them.In the late 1950s, to mid '60s, if you did any formal course in Semiconductors at Technician level, you learnt about such things as Valency bonds, Electron energy levels, & so on.It seemed that the Physicists didn't know how much to "dumb" things down before passing it on to the EEs, who in turn, passed it pretty much untouched to the Techs.Your information dates from this period.As the Physicists used Electrons & "holes", so did the material, which usually showed current as Electron Flow.This was hardly a problem, as there were thousands of people to whom Electron Flow was not something "new & alarming", but how current flowed through vacuum tubes, & external circuitry.At the same time, such people happily used Conventional Current Flow for calculations appertaining to motors, generators, electromagnets, etc, due to the vast quantity of material, "Right Hand Rules", & so on, available using CCF, which hadn't yet attained the "god-like" status it enjoys today amongst many.Any information presented in that period as part of a Semiconductor course was most likely to use EF.A lot of the stuff was interesting, but not really used every day, as circuit applications were not usually covered very intensively.Many years later, as part of another course, I did a unit which went seriously into circuit theory, ignoring Semiconductor Physics, & effectively treating the transistor as a "black box".This used CCF, which didn't worry me in the least, but was much more useful in understanding theuseof such devices.Many of the design formulas are either the same, or similar between BJTs, FETs, & vacuum tubes.

author: TimFox
author_rank: Super Contributor
timestamp: January 04, 2020, 03:27:58 pm
content: The only places where I saw "electron flow current" taught instead of "conventional current" were several military electronics textbooks, from the vacuum-tube era, that were given to me as a kid by friends of the family who were veterans. In my physics and electronics education, it was always conventional current and signed charge carriers (electrons, ions, holes, etc.)

author: GlennSprigg
author_rank: Super Contributor
timestamp: January 05, 2020, 02:17:34 pm
content: "And this sacred valley here was formed by the giant snake that wormed it's way..."Some people might believe that, for fun, (or pity them...) when we were impressionistic children.Just because "Conventional Flow" was all that they understood at the TIME, has ZERO reasonwhy this preposterous notion should be even discussed in this day & age !!!The only underlying 'convention' is Diagrams of old, and device symbols. It has NO place today!!

author: madires
author_rank: Super Contributor
timestamp: January 05, 2020, 03:48:53 pm
content: Just saying, there are also conductors with positive charge carriers, e.g. solid electrolytes with H+ charge carriers.