Justin Bell Perhaps, if I do another video on the differences between enhancement & depletion mode MOSFET's and JFET, then I guess I might as well include IGBT's.
I used to work at IBM making microprocessors. When you described the MOSFET gate operation, I was reminded of how much time our engineers spent perfecting the gate oxide layer. There were 40 PHD level engineers working full time on gate oxide quality. Good oxide equals faster speed. The more expensive fast CPU processor is identical to the cheaper CPU except for the quality of the gate oxide.
@@charlesclements4350 there are a few vid out there. the most interesting is those using a high magnification microscope to look at processor circuitry.
@@charlesclements4350 It's an awesome process. I worked at a company called Atmel that made alot of ASIC parts then mostly EEPROMS and 8bit MCU's along with a host of other stuff. I was the lead operator for the strip process cleaning the silicon in preparation for the next step. The inspection post cleaning was to me the most amazing. Watching the layers build up. Did quite a bit of inspect during the metal layers as well .... DId get to use a Scanning Electron Microscope ( when I became an Eng. Tech ) that was the best. Also got, at various times, to get cross section views when trying to determine what / where contamination was located.
I've just started studying electrical engineering and I don't get the textbook and I never understand anything on the lectures, so each time i have a test or a laboration I just look at your videos and suddenly I'm the *smartest* one in the room, despite knowing nothing and feeling devastated just hours before. You've literally saved me from failing and even helped me get better grades than I thought was possible. You are the best teacher and I wish the best for you.
Frankly, there is no better lecture on the interent, almost none goes this deep to explain how the elctrons and holes work, after searching for a week to understand it and reading books this one is the best.
A decent addition to the world's collection of videos explaining how transistors work. Maybe it's just me, but I think the FET is a little easier to understand how it works.
That is a very clear explaination. And the time you needed is not much at all. Had the same stuff at school decades ago but it took the teacher 1.5 full hours to explain. Well done.
This extra electron appearing in doped matrix was brilliantly explained. I've never seen it done graphically, it still makes sens without the picture, but this way it is really easy to understand and remember.
Nice!! These are my favorite videos of yours. You did one similar with op amps. I absolutely love these. They are the reason I subscribe. Thanks so much!
gamingSlasher Ah, yeah, could have made that better. Basically, small number of holes enter from the base, huge number of free electrons get moved up from the emitter due to the collector voltage, and only some of those electrons match up with holes to exit the base. the rest go up to the collector. Hence small base current, large collector current.
Never commented on your videos before but I've been watching this channel for over a year so I thought I'd write one now: EEVblog is full of great insights into electrical engineering, and Fundamentals Friday is my favourite segment. From and inspired by it I have learned a lot of electronics basics. I wish my teachers would've been as inspiring as you are. Maybe I would have gotten into electronics earlier. Electronics for me have turned from a hobby into a job and I'm loving every moment of it. Keep making these videos. You rock! Sincerely, Panu
Fantastic video, with probably the clearest explanation I have seen so far on this topic. It is something that is actually difficult to teach and you did great!
I would LOVE to see a nice video about how to drive MOSFETS and BJT, including high currents, and inductive loads with "soft off" AWESOME video!!! Learned a lot! Thanks!
Thanks a lot Dave for your work and your time! I deeply respect people like you who take their time to spread their knowledge free. Of course, some "Iknoweverythingandimbetterthanyou" people will criticize your work, but what you do is popularization of electronic sciences (and you never claimed it to be anything else, and... no one's perfect). So thank you again! BTW, if i may, you should do also a thursday, wednesday or whatever day lesson, where you present and explain, in a 5 minutes format, week after week, a simple electronic circuit function: example like limiter current system, protection system, etc... but kind of circuit that you build with less than 10 basic components (resistor, transistor, capacitor, diode, even AOP in the most extreme case), not the one that you build round with a specialized IC.
definitely interested in more vids about how semiconductor devices work! I've been having a little trouble fully grasping how they work, but your detailed descriptions with visual aids definitely clarify things nicely.
very nice video. I spent hours and hours to try to understand the principle and I felt exhausted and depressed. Your TH-cam can make me understand within a hour.!
I have worked in electronics, both as a career and as a hobby for more than 40 years. Even after reading several articles and books about how transistors work (remember the old RCA transistor manual?), I never really understood it as clearly as your explanation here. Thanks.
Awesome video. You explained this better in 20 minutes than my EE professor did in multiple weeks worth of classes. I think university professors need to lay off the math and explain things like this. When they just want to jump into calculations and numbers they fail to explain the greater picture like you do here.
I've always wanted to know the difference between BJT and Mosfets and this video explains that and even more! Thanks Dave and Keep the great videos coming!
Great review of stuff I began to learn over 50 years ago as a naive young-ling. But I still love to review it and imagine all of the little particles in there doing my bidding within my amplifiers...
my teachers could never explain a transistor this clearly. as a result ive been afraid to design circuits with them because of the PFM (pure f__ing magic) associated with their operation. thank you
I think what happens is that the electron moves over, and thus the atom left behind is now genuinely positively charged. Obviously the P type silicon wants to have that extra electron to fill its shell, but technically it is neutrally charged, and the N type wants that extra electron gone from its shell, but is also still neutral. When they meet up and the electrons go from the N type to the P type, they happily fix their she'll situation, but the result is that now you literally have a negative charge on the P type and a positive on the N type. It's almost like the "holes" did move over. Technically of course the situation is fundamentally different, but from an engineering point of view you don't need to care about that, you can just say the two materials swapped roles.
If this was taught at my university like this, I would surely be more curious back then when I was younger. We were all about smoking resistors and blowing caps.
When I trained with the P.M.G. in the sixties we were taught that the old conventions were wrong, that current flowed from -ve to +ve and that electron flow was the new future in electronics. Easily understood and remembered when you study the operation of a vacuum tube amplifier. At the same time, Cycles per Second (CPS) was being dispensed with and replaced with Hz (in honour of Hertz). Voltage was to be represented by E (for electromotive force) in lieu of V. So, I = E / R. Out with the old and in with the new. Hole movement was theorectical, the electrons moved into the holes leaving holes behind them. In a theatre, there's an empty seat (hole) at the far end of the row. Instead of the new patron (electron) stumbing all the way down the row, it's easier for everyone in the row to move to an adjacent seat. The empty seat (hole) effectively moves to the other end of the row but it's really the patrons (electrons) that are moving. Without a discussion of manufacture and the actual fusing together of the PN layers in an oven, there is no clear understanding here of how the depletion layer forms. These aren't pieces of silicon that are just placed next to each other, they are FUSED. The depletion layer creates an actual potential difference that must be overcome by external forces before current can begin to flow. When and why did the electronics industry revert from the NEW sixties conventions and decide to fall back to confusing ancient conventional current flow and also, bring back "V"?
Dave wisely avoided the confusion surrounding the direction of the arrow. Scientists at Bell Labs incorrectly depicted "conventional flow" (plus to minus) when everyone who has ever worked with vacuum tubes knows that electron flow is from minus to plus.
awesome video! i'm about a month into my circuits 1 course at university and this video is very helpful at helping me understand how transistors work! Hopefully a bit more practice with the calculations and i'll have these things down for the test in 2 weeks.
Nice video Dave! I think it would be nice to illustrate why Mosfet can be connected in parallel without worries while for BJT one should always use ballasting resistors.
Please do a followup video about popular transistor configurations, basic building blocks. Many people struggle with that. I've done several commercial designs and still could use a revision.
5:29 Having the same amount of protons and neutrons does not make it have a neutral charge! Neutrons are neutrally charged so they cannot balance the positively charged protons! Was shouting at the screen lol EEVblog
waicool20 Doh, did I really say that? - Yup, I did! Fixed in annotation, thanks. I shouldn't have put the neutron count in the middle, that's a tad confusing.
Just want to point out that the doping on the collector side is light, not heavy. Normally, the doping level is as such: Emitter >> Base > Collector. This is so that when in reverse bias, there won't be a large current flow. If you make a symmetrical BJT, then forward and reverse bias will cause same current flow magnitude.
The process of understand is what physics does, but our electronics lecturer teaches only math. Been searching these videos for months. Very good work. Better go into classifications and calculations of V,I, etc in another video.
I really hope this Fundamentals Friday becomes a more frequent series, and covers subjects of 101 electronics engineering, though I know how busy Dave is... thanks anyway..
Excellent video Dave!! Could you please make a video explaining the manufacturing steps required to produce a transistor/mosfet? For example how do you dope silicon? How are the channels etched? How is the insulating oxide layer created? How are the metal contacts deposited?
Hi Dave, first thanks for all your awesome videos, not only this one. As a small suggestion, the MOSFET it's easier to understand if the 4th terminal (often not shown) is included and conected to the source terminal, so the electric field is applied to the whole substrate creating the conductive channel
THIS is educational!!! When you break things down to their simplest form and begin rebuilding them until you have a component, the principles of electronics really become evident! Tired issues, like which type of capacitor is "best," become rubbish. Does that cap allow the electron to move from one atom to another? More efficiently than another? I spend WAY to much time listening to the information Dave shares!!! Back to the money square, I go!!!
"Deeptails" is one of my new favourite words ;-) This reminds me a little of my old greybeard colleague getting excited when I ask him about valves, and he proceeds to draw me a mini-lecture on my lab whiteboard :D
I did a presentation on transistors as part of my Masters. I was in a team with other electrical engineers so it did not take much convincing to get them to take the idea on.
Hello Dave: I have been watching and learning from many of your videos for the past 10 years and I wanted to take the time out to thank you for the Excellent job of explaining in great detail. I am now retired currently residing as an expatriate with my Philippine born wife in the Philippines. I have 50 years of experience in the field of electronics and electrical almost all phases from power plant, industrial controls, consumer electronics including Tv repair, computer systems and residential and commercial electrical wiring just to mention a few. This experience comes along with vast amount of Technical, Vocational, Military and collegiate education. I would particularly like to mention your video on the TD- 220 Tektronix Digital scope where you were shown reviving one you had found in the mud lol! I happen to have one along with a few others. I decided to pull it out a few days ago for use in troubleshooting a problem to find that the LCD display has gone bad only able to view some traces of letters and figures at high contrast. Well just thought I’d share that with you and let you know you are doing an amazing job. Keep those videos coming.
And for those who thinks this is the best explanation they have ever seen, I recommend you to read Shockley's original book on the subject "Electrons and Holes in Semiconductors with Applications to Transistor Electronics" or Chenming Hu's "Modern Semiconductor Devices for Integrated Circuits"
Thanks Dave for the great video. Not sure if it's been covered or not yet, but like Intel & AMD years ago when clock speeds basically topped out, but they kept naming their CPUs with "virtual" clock speeds representing the effective performance improvements due to other innovations like multi-threading and multi-core, the semiconductor industry has been doing the same for the past several generations. So the 14nm node does not literally have a channel length of 14nm, the transistor performance just behaves as if it did. The really impressive dimension though is the gate oxide thickness, which actually is only a few atoms thick, and controlling this thickness (much less reducing it) is one of the main motivating factors behind going to the FINFET non-planar transistor design for 14nm.
Congratulations.Thank you for sharing your knowledge with us.Very good English speech,good for non native English speakers .Keep going. Do you plan a video for Depletion type FET transistors?
There's this book "Horowitz and Hill." Not familiar? You do realize that it contradicts this above BJT explanation. They repeatedly show that BJTs are voltage driven. H&H's book AOA steers students away from "current driven" by giving many examples of broken circuits which were created with the "current input" BJT misconception. The lab book for Horowitz and Hill goes even more into this. They show that slight temperature changes screw up the hfe-based circuits, and totally halt function because of device-to-device variations. hfe-based transistor stages each need a trimpot and a thermistor. Vbe-based designs do not. Then, AOA points out the many circuits which are impossible if transistors are current amplifiers, but which are easily explained if they're voltage amps: impossible things like BJT op-amp front ends! Why aren't BJT op amps based on current-input? Because BJTs are inherently voltage in, current out, and their base terminals need no resistor in series. Also: the bjt CB junction is not thin, that's wrong. That junction always has a relatively thick depletion layer, and it never gets thin. In fact, the higher the supply-voltage, the wider is that depletion zone. But electrons easily flow across it because they're being dumped on the wrong side! They see the wide empty zone as a vacuum, and easily cross it, driven by the strong e-fields in that insulator region. The wide BC junction acts a lot like the vacuum in a vacuum tube; it's insulating unless an electron cloud is supplied.
+wbeaty There is no misconception other than to say that in the absence of voltage there is an absence of current. There is also a book written by Bill Shockley who was probably a lot smarter than Horowitz and Hill put together. I should probably say that either Horowitz or Hill individually is a lot smarter than I, but we have to pick our gurus based on something.
+Richard Gray Of course there's a misconception. This error is exposed in any engineering classroom, especially in the semiconductor physics classes. The error isn't only debunked in AOA book, but everywhere. AOA is just an easily-recognizable example. The above video about BJT operation is oversimplified and wrong, using concepts typically aimed at low-level techs who don't need to do actual BJT designs. If you have no desire to understand the silicon itself, a wrong explanation won't hurt you. But the wrong explanation isn't necessary, since this "analog engineers' secret" isn't that complicated. But it does require that we confront and defeat the wrong concepts we've been taught. Many people won't do that ever. They prefer to believe that grade-school textbooks tell the truth, just like George Washington chopping down the cherry tree, and heroic Columbus who would never think of murdering or enslaving the natives. So, what's the "Lies to Children" part of transistor explanation? It's the mistaken idea that base current Ib can control collector current Ic. To understand transistors' internal function, we must note that the base current has *no direct effect* on collector current. One current cannot affect another. Instead, the entire base circuit sets the value for base voltage Vbe (via the Shockley equation of course.) Then the Vbe potential-barrier determines both currents: Ib and Ic. We can view this as Ib affects Vbe which then affects Ic ...and then we can go further and form a simplified 'black box', where Ib apparently determines Ic directly. But, if we open the hood and look inside, we find that BJTs are voltage-input devices, transconductance devices same as FETs, where the ruling equation is Ie=Is*e^Vbe/nkt -Is. This isn't that complicated! It's just transconductance: volts in and current out. Same as FETs and vacuum tubes. But we do need to have high-school algebra, so we're not scared off by nasty math like the diode exponential equation. And we must face the terrible horrible fact that Vbe is not actually fixed at 0.7v, and it never was. (Oh no!) :) All of BJT-engineering is based on this Shockley equation, the Ebers-Moll version, where base voltage determines Ie and Ic. It's why BJT op-amps have voltage input rather than Ib current input. In op amps, the differential-pair front end is a voltage-input transconductance circuit. (For those who believe in BJT current-input, the long-tailed pair circuit remains a deep and confounding mystery!) The breakthrough to understanding op-amp internals is easy: BJTs are voltage input animals, and your earlier teachers were wrong about the nature of hfe. Also, base-voltage is how current-mirrors work, and half the stuff inside any analog IC is the current-mirrors replacing the large resistors. Try explaining current mirrors or Cascode circuit based on hfe, where Vbe is fixed. Not possible. Of course it's fine to use Ic=hfe*Ib in many situations. It's an extremely useful simplified rule of thumb, like Ohm's law. Just don't try to use it to explain the internal physics of components, or everything gets loopy and distorted. Yes, Shockley himself was beating the drum for "BJTs are current input." He was wrong, but had VERY good reason. His statement appears to be Bell Tel business-hype, done to make certain that USPTO wouldn't reject BJT patent applications, since voltage-input Lilienfeld transistors had already been patented twenty years earlier. Bell Labs had to distance themselves somehow from existing FETs. A good way to do this is to pretend that BJTs are current-input while FETs are voltage input. But it's not honest science (though it may be honest cutthroat business practice.) BJTs use voltage-input and use the (ahem!) Shockley Equation. Shockley worked out the whole semiconductor theory behind them. So, why would he claim that BJTs are current-input when he very well knew that they weren't? If he hadn't, there might not be any Bell Tel transistors; no patent, no profit, no aerospace contracts. Yet his small businessmans-lie is confusing-the-noobs even today. They just have to take some college undergrad courses to get the "hfe stuff" beaten out of them, and learn to slap on that Vbe Shockley equation just as easily as using Ohm's law.
+wbeaty Puhleeze. There is nothing wrong-headed about modeling a bipolar transistor using collector current as a function of base current. But, if you KNOW better than that, then I'm happy for you.
+Richard Gray Yes, that's a lot like modeling diodes as having fixed 0.7V voltage: often useful, even though certain designs would fail. And of course it tells us little about how diodes work inside. The "current amplifier" model of transistors is fine as long as we know that it's just an ultra-simplified black-box model. Major trouble arises whenever people think it's really true, and then they try to base designs on it. The designs don't work (their resistors have to be hand-adjusted for each transistor used, and temperature effects are enormous, requiring thermistor compensation circuits.) Also, classroom trouble crops up when we try to explain such things as Op-amp basics. The op-amp diff-input front-end relies upon base voltage signals, not on hfe, and it cannot be explained in terms of current-amplifier transistors. --- I encountered this problem myself, on a very first professional analog design for an industrial opto-sensor. I was forced to abandon the current-based "hfe-think"; and instead spreadsheeted everything as voltage-input (transconductance) circuits where hfe is ignored. Worked fine. That sensor design is in coke machines everywhere. Win Hill, one of the authors of "Art of Electronics" tells exactly the same story here: cr4.globalspec.com/comment/720374/Re-Voltage-vs-Current Before he could succeed at circuit design, first a wise old engineer had to take him aside and teach voltage-centric BJT philosophy, as opposed to the "current amplifier" stuff he'd learned in early schooling. So, instead of first being taught that BJTs use current input, why don't we just do an end-run instead? Never learn hfe stuff at all, but directly jump into teaching that BJTs are voltage-input devices like FETs? After all, that's what they really are. But then we'll have to face the fact that our earliest teachers were lying when they taught us that George Washington chopped down a cherry tree, or that Columbus was a saintlike hero, or that BJT transistors are current amplifiers. Or that William Schockley cannot tell a lie! :)
+wbeaty Well, I knew as a second-grader that it was bullshit when my teacher told us that George Washington never told a lie or as a seventh-grader when we were told that Isaac Newton watched an apple fall and thus invented gravity. But, later, I never got that feeling about hfe being a useful device parameter.
hell yeah you explained it better...in fact better as my university professor :))) one of them told us that the nm it the size of the transistor(capsule) not the distance between channels
From what I know those symbols were created because of conventional current flow. Anyway, nevermind that. I don't understand why does it make more sense... I'm really curious.
ronettreker Water runs downhill, from the higher up potential to the lower potential for example. Thing like that make conventional current more relate-able and more "obvious" that current flows from positive to negative. That's why they thought that was the case to begin with, it wasn't an arbitrary choice.
EEVblog Isn't the number of electrons in a medium that define it's potential? I thought that electrons flow from a medium wich contains more free electrons to a medium which contain less, in order to achieve equilibrium. I thought the reason why the higher potential medium is negative is because of the higher number of negatively charged electrons. If so, then the negatively charged medium is the one with higher potential, not the positively charged one. Did I got it right?
ronettreker i think you may be missing the point I was trying to make. I was trying to show how (unless you know the details) it's more obvious to the lay person that something (current) would flow from something higher (potential) to lower (potential).
Thanks for the video, but there is one misunderstanding. 15:50. The depletion region is formed by the negative ions in the p-type/substrate side and the positive ions in the n-type (source) side, not electrons and holes like what you mentioned. The negative ions (acceptors) are created in the p-type/substrate side due to the gain of electrons diffused from n-type, whereas the positive ions (donors) are created in the n-type/source side due to the loss of the electrons which diffuses to the p-type/substrate side. Hope you can add notes there (15:50) to not let people misunderstand this. Thanks.
Literally the best lecture on semiconductors I've ever seen.
Afrotechmods Yeah, I like your channel too, Please make more vids :-).
Afrotechmods Thanks! I'm sure there are much better technical explanations out there though.
EEVblog Do you plan to do a video on IGBTs?
Justin Bell Perhaps, if I do another video on the differences between enhancement & depletion mode MOSFET's and JFET, then I guess I might as well include IGBT's.
Agreed. I need more information that, "here's this and here's how you use it." I want to know why it works. This is the perfect deep-dive.
I used to work at IBM making microprocessors. When you described the MOSFET gate operation, I was reminded of how much time our engineers spent perfecting the gate oxide layer. There were 40 PHD level engineers working full time on gate oxide quality. Good oxide equals faster speed. The more expensive fast CPU processor is identical to the cheaper CPU except for the quality of the gate oxide.
Now that you mentioned it, Jeff, just how are those things built? Did any of you make a video of what goes on in a plant where those things are made?
@@charlesclements4350 there are a few vid out there. the most interesting is those using a high magnification microscope to look at processor circuitry.
Wow ! Thanks, tbled52, I'll keep my eyes open for them.
Respect
@@charlesclements4350 It's an awesome process. I worked at a company called Atmel that made alot of ASIC parts then mostly EEPROMS and 8bit MCU's along with a host of other stuff.
I was the lead operator for the strip process cleaning the silicon in preparation for the next step. The inspection post cleaning was to me the most amazing. Watching the layers build up. Did quite a bit of inspect during the metal layers as well .... DId get to use a Scanning Electron Microscope ( when I became an Eng. Tech ) that was the best.
Also got, at various times, to get cross section views when trying to determine what / where contamination was located.
The clearest explanation of how transistors work I have ever seen. Thanks Dave!
dogastus Thanks, glad it was understandable for you.
Agreed, and I did 2 years of micro-electronics specialization, and spent countless hours making diodes and transistors and logic gate in the lab
dogastus Entirely agreed. This is fantastic.
good job
I learned more in this 23 minute video than I did during an entire semester of my semiconductors course in college. Well done!
You explained in 10 minutes what took a whole semester in college... and I actually understand it better. Well done.
I've just started studying electrical engineering and I don't get the textbook and I never understand anything on the lectures, so each time i have a test or a laboration I just look at your videos and suddenly I'm the *smartest* one in the room, despite knowing nothing and feeling devastated just hours before. You've literally saved me from failing and even helped me get better grades than I thought was possible. You are the best teacher and I wish the best for you.
Have you finished your degree?
Frankly, there is no better lecture on the interent, almost none goes this deep to explain how the elctrons and holes work, after searching for a week to understand it and reading books this one is the best.
Thanks for taking the time to make this video. I have learned something new today and you're responsible for that.
just by you lightly mentioning the ACTUAL flow of electrons, you have started a great avalanche of debate about this issue. Good stuff.
This video should be required viewing in all basic electronic courses. Very well done, Dave.
I love how you specifically distinguish conventional current and electron flow. Fabulous!
Best lesson on semi-conductors I've experienced online or in class. Thanks EEVlog!
Yeah! It seems like they want you to know all of the math, instead of practical theory, and applications.
A decent addition to the world's collection of videos explaining how transistors work.
Maybe it's just me, but I think the FET is a little easier to understand how it works.
+EEVBlog, that's the best explanation ever, textbook authors should learn how to do this from this one! Massive thumbs-up! Thx!
That is a very clear explaination. And the time you needed is not much at all. Had the same stuff at school decades ago but it took the teacher 1.5 full hours to explain. Well done.
i made a whole project about bjt's and mosfets in middle school. learned more by watching this video than when i did that project. well done lol
This extra electron appearing in doped matrix was brilliantly explained. I've never seen it done graphically, it still makes sens without the picture, but this way it is really easy to understand and remember.
Nice!! These are my favorite videos of yours. You did one similar with op amps.
I absolutely love these. They are the reason I subscribe.
Thanks so much!
Very good presentation. The only difficult thing was the explanation of the current amplifying physics. That was unclear. The mosfet was very clear.
gamingSlasher Ah, yeah, could have made that better. Basically, small number of holes enter from the base, huge number of free electrons get moved up from the emitter due to the collector voltage, and only some of those electrons match up with holes to exit the base. the rest go up to the collector. Hence small base current, large collector current.
Easily the clearest explanation of transistors I've seen. Thanks!
Never commented on your videos before but I've been watching this channel for over a year so I thought I'd write one now:
EEVblog is full of great insights into electrical engineering, and Fundamentals Friday is my favourite segment. From and inspired by it I have learned a lot of electronics basics. I wish my teachers would've been as inspiring as you are. Maybe I would have gotten into electronics earlier. Electronics for me have turned from a hobby into a job and I'm loving every moment of it. Keep making these videos. You rock!
Sincerely,
Panu
Fantastic video, with probably the clearest explanation I have seen so far on this topic. It is something that is actually difficult to teach and you did great!
I would LOVE to see a nice video about how to drive MOSFETS and BJT, including high currents, and inductive loads with "soft off" AWESOME video!!! Learned a lot! Thanks!
You taught me in 20 min what my professor tried to teach me in 2 weeks. Nice Video!
Moore's law is nonsense.
I put a transistor into my drawer 10 years ago and it did not become smaller at all.
The Kaiser Hahaha. You are hilarious.
The Kaiser Hahaha. You are hilarious.
The Kaiser I remember putting a transistor in a drawer 10 years ago. I just went to look and I had 32 transistors, just what I expected.
mart fart It is about getting smaller, NOT more and I bet you left 2 transistors of opposite sex in the drawer, so that was to be expected.
+The Kaiser mine became mosfets, as expected. Measure emitter-base, and its open in both directions.
You explained it way better than my Iranian instructor(No Bias), back in the day, Dave. Many thanks!
Thanks a lot Dave for your work and your time! I deeply respect people like you who take their time to spread their knowledge free. Of course, some "Iknoweverythingandimbetterthanyou" people will criticize your work, but what you do is popularization of electronic sciences (and you never claimed it to be anything else, and... no one's perfect). So thank you again!
BTW, if i may, you should do also a thursday, wednesday or whatever day lesson, where you present and explain, in a 5 minutes format, week after week, a simple electronic circuit function: example like limiter current system, protection system, etc... but kind of circuit that you build with less than 10 basic components (resistor, transistor, capacitor, diode, even AOP in the most extreme case), not the one that you build round with a specialized IC.
You upload this video just a few days after my exam in the subject!!
Yr 12 physics exam on monday, one section is transistors. You couldn't have timed this better
Thank you so much for this, Dave!
I have struggled to understand how transistors really work for years, and you completely cleared it up for me!
Hamstah Glad to hear!, thanks.
definitely interested in more vids about how semiconductor devices work! I've been having a little trouble fully grasping how they work, but your detailed descriptions with visual aids definitely clarify things nicely.
very nice video.
I spent hours and hours to try to understand the principle and I felt exhausted and depressed. Your TH-cam can make me understand within a hour.!
Very well simplified and explained the solid-state-physics things less than 24 min.
Well done!
Is anyone else interested in a Fundamental Friday explaining the different physics involved with vacuum tubes compared to transistors?
I've always been confused at the difference between the two, this explains it very well.
Finally someone who speaks clear English and knows what they are talking about.
I have worked in electronics, both as a career and as a hobby for more than 40 years. Even after reading several articles and books about how transistors work (remember the old RCA transistor manual?), I never really understood it as clearly as your explanation here. Thanks.
Awesome video. You explained this better in 20 minutes than my EE professor did in multiple weeks worth of classes. I think university professors need to lay off the math and explain things like this. When they just want to jump into calculations and numbers they fail to explain the greater picture like you do here.
I think they might first explain it like dave and then go to the maths.
This is very exact problem I have in my studies.
Omg YES!
Also try having professors who barely speak English.
I've always wanted to know the difference between BJT and Mosfets and this video explains that and even more!
Thanks Dave and Keep the great videos coming!
Awesome dive into into the physical world of transistors!
Dave would make an awesome classroom instructor!
Great review of stuff I began to learn over 50 years ago as a naive young-ling. But I still love to review it and imagine all of the little particles in there doing my bidding within my amplifiers...
my teachers could never explain a transistor this clearly. as a result ive been afraid to design circuits with them because of the PFM (pure f__ing magic) associated with their operation. thank you
Thumbs up Dave, just like the lectures I went through at University.
This is really useful. Even for people who work with this regularly to be able to explain it to other people. Thanks!
I think what happens is that the electron moves over, and thus the atom left behind is now genuinely positively charged. Obviously the P type silicon wants to have that extra electron to fill its shell, but technically it is neutrally charged, and the N type wants that extra electron gone from its shell, but is also still neutral. When they meet up and the electrons go from the N type to the P type, they happily fix their she'll situation, but the result is that now you literally have a negative charge on the P type and a positive on the N type. It's almost like the "holes" did move over. Technically of course the situation is fundamentally different, but from an engineering point of view you don't need to care about that, you can just say the two materials swapped roles.
Many thanks for another trip back to basic EE stuff. Actually, a bit of physics as well.
Excellent.
If this was taught at my university like this, I would surely be more curious back then when I was younger. We were all about smoking resistors and blowing caps.
When I trained with the P.M.G. in the sixties we were taught that the old conventions were wrong, that current flowed from -ve to +ve and that electron flow was the new future in electronics. Easily understood and remembered when you study the operation of a vacuum tube amplifier. At the same time, Cycles per Second (CPS) was being dispensed with and replaced with Hz (in honour of Hertz). Voltage was to be represented by E (for electromotive force) in lieu of V. So, I = E / R. Out with the old and in with the new. Hole movement was theorectical, the electrons moved into the holes leaving holes behind them. In a theatre, there's an empty seat (hole) at the far end of the row. Instead of the new patron (electron) stumbing all the way down the row, it's easier for everyone in the row to move to an adjacent seat. The empty seat (hole) effectively moves to the other end of the row but it's really the patrons (electrons) that are moving. Without a discussion of manufacture and the actual fusing together of the PN layers in an oven, there is no clear understanding here of how the depletion layer forms. These aren't pieces of silicon that are just placed next to each other, they are FUSED. The depletion layer creates an actual potential difference that must be overcome by external forces before current can begin to flow. When and why did the electronics industry revert from the NEW sixties conventions and decide to fall back to confusing ancient conventional current flow and also, bring back "V"?
!!!!!! Thank You !!!!! For Bridging the gap on a 20 year mystery
Dave wisely avoided the confusion surrounding the direction of the arrow. Scientists at Bell Labs incorrectly depicted "conventional flow" (plus to minus) when everyone who has ever worked with vacuum tubes knows that electron flow is from minus to plus.
awesome video! i'm about a month into my circuits 1 course at university and this video is very helpful at helping me understand how transistors work! Hopefully a bit more practice with the calculations and i'll have these things down for the test in 2 weeks.
Nice video Dave!
I think it would be nice to illustrate why Mosfet can be connected in parallel without worries while for BJT one should always use ballasting resistors.
Please do a followup video about popular transistor configurations, basic building blocks. Many people struggle with that. I've done several commercial designs and still could use a revision.
This was awesome. Thank you very much! I had that "Ah-Ha!" moment here where it all clicked.
you had an A-Ha Moment and you decided to TAKE HIM ON huh ? LOL
5:29 Having the same amount of protons and neutrons does not make it have a neutral charge! Neutrons are neutrally charged so they cannot balance the positively charged protons! Was shouting at the screen lol EEVblog
waicool20 Doh, did I really say that? - Yup, I did! Fixed in annotation, thanks. I shouldn't have put the neutron count in the middle, that's a tad confusing.
Great, Thanks! I'm stil struggling with the BJT, but I guess I'll just look at it again until I get it.
Just want to point out that the doping on the collector side is light, not heavy. Normally, the doping level is as such: Emitter >> Base > Collector. This is so that when in reverse bias, there won't be a large current flow. If you make a symmetrical BJT, then forward and reverse bias will cause same current flow magnitude.
this is great, we did this on the physics level today at uni, thanks dave. :)
Mind-boggling I love the way you explain it makes it a little bit easier for someone like me to try and understand many thanks👍
The process of understand is what physics does, but our electronics lecturer teaches only math. Been searching these videos for months.
Very good work. Better go into classifications and calculations of V,I, etc in another video.
I really hope this Fundamentals Friday becomes a more frequent series, and covers subjects of 101 electronics engineering, though I know how busy Dave is... thanks anyway..
Very good explanation. FETs are new since I studied Physical Electronics in the 60's!
Excellent video Dave!!
Could you please make a video explaining the manufacturing steps required to produce a transistor/mosfet? For example how do you dope silicon? How are the channels etched? How is the insulating oxide layer created? How are the metal contacts deposited?
Hi Dave, first thanks for all your awesome videos, not only this one.
As a small suggestion, the MOSFET it's easier to understand if the 4th terminal (often not shown) is included and conected to the source terminal, so the electric field is applied to the whole substrate creating the conductive channel
THIS is educational!!! When you break things down to their simplest form and begin rebuilding them until you have a component, the principles of electronics really become evident!
Tired issues, like which type of capacitor is "best," become rubbish. Does that cap allow the electron to move from one atom to another? More efficiently than another?
I spend WAY to much time listening to the information Dave shares!!! Back to the money square, I go!!!
Yes, I like fundamentals in Dave's way.
Clear as mud : )
Man oh man
Couldn't have explained it better
My hat is off to you :)
One of your best videos Dave. First thing that comes time mind is you should write books but these videos are far more effective.
Thanks Dave, looking forward to more videos like this....total beginner here
"Deeptails" is one of my new favourite words ;-) This reminds me a little of my old greybeard colleague getting excited when I ask him about valves, and he proceeds to draw me a mini-lecture on my lab whiteboard :D
Thank you so much! This was very informative and detailed. I loved the Moore’s law explanation at the end.
This is an excellent presentation Dave, well done.
Dave, you are a great instructor, brother!
Absolutely Superb!! Best explanation I've seen.
Moreover Australian accent made it just PERFECT!!
Thank you mate!!
I did a presentation on transistors as part of my Masters. I was in a team with other electrical engineers so it did not take much convincing to get them to take the idea on.
Hello Dave: I have been watching and learning from many of your videos for the past 10 years and I wanted to take the time out to thank you for the Excellent job of explaining in great detail. I am now retired currently residing as an expatriate with my Philippine born wife in the Philippines. I have 50 years of experience in the field of electronics and electrical almost all phases from power plant, industrial controls, consumer electronics including Tv repair, computer systems and residential and commercial electrical wiring just to mention a few. This experience comes along with vast amount of Technical, Vocational, Military and collegiate education. I would particularly like to mention your video on the TD- 220 Tektronix Digital scope where you were shown reviving one you had found in the mud lol! I happen to have one along with a few others. I decided to pull it out a few days ago for use in troubleshooting a problem to find that the LCD display has gone bad only able to view some traces of letters and figures at high contrast. Well just thought I’d share that with you and let you know you are doing an amazing job. Keep those videos coming.
And for those who thinks this is the best explanation they have ever seen, I recommend you to read Shockley's original book on the subject
"Electrons and Holes in Semiconductors with Applications to Transistor Electronics"
or
Chenming Hu's
"Modern Semiconductor Devices for Integrated Circuits"
I now understand about P, N, and how transistors work. Why couldn't anyone else explain it to me this clearly?
Great video, Dave! Would love to see more educational videos like this.
Love to see a video on using glue logic chips to create a simple circuit, holding and switching state type stuff.
Thanks Dave for the great video. Not sure if it's been covered or not yet, but like Intel & AMD years ago when clock speeds basically topped out, but they kept naming their CPUs with "virtual" clock speeds representing the effective performance improvements due to other innovations like multi-threading and multi-core, the semiconductor industry has been doing the same for the past several generations. So the 14nm node does not literally have a channel length of 14nm, the transistor performance just behaves as if it did. The really impressive dimension though is the gate oxide thickness, which actually is only a few atoms thick, and controlling this thickness (much less reducing it) is one of the main motivating factors behind going to the FINFET non-planar transistor design for 14nm.
I need more Fundamental Friday in my feed...
Great videos! Appreciate the level and detail you give when explaining.
Thank you very much for that wonder explanation. You answered many questions that I was pondering on.
I've finally understood transistors. Thank you
Current flow = charge flow flow. Ugh. Other than that, takes me back to my days in chemistry class.
Fantastic video, BJT's really are such wonderful devices
Congratulations.Thank you for sharing your knowledge with us.Very good English speech,good for non native English speakers .Keep going.
Do you plan a video for Depletion type FET transistors?
Great video, thanks for the thorough but perfectly ELI5'ed explanation! Now I'm really a FULL-stack engineer. :)
Dave, you are the engineer par excellence, I love fundamental Fridays, I really learned something. thanks you are DA Man!!!
Perfect, unsurpassed explanation, thank you very much indeed
I wish I could upvote this more than once.
Fundamental Friday wins again. Thanks, Dave!
Nice tutorial on Transistors.
It will be great if you can have some videos on AM, FM, RF controls etc...
There's this book "Horowitz and Hill." Not familiar? You do realize that it contradicts this above BJT explanation. They repeatedly show that BJTs are voltage driven.
H&H's book AOA steers students away from "current driven" by giving many examples of broken circuits which were created with the "current input" BJT misconception. The lab book for Horowitz and Hill goes even more into this. They show that slight temperature changes screw up the hfe-based circuits, and totally halt function because of device-to-device variations. hfe-based transistor stages each need a trimpot and a thermistor. Vbe-based designs do not. Then, AOA points out the many circuits which are impossible if transistors are current amplifiers, but which are easily explained if they're voltage amps: impossible things like BJT op-amp front ends! Why aren't BJT op amps based on current-input? Because BJTs are inherently voltage in, current out, and their base terminals need no resistor in series.
Also: the bjt CB junction is not thin, that's wrong. That junction always has a relatively thick depletion layer, and it never gets thin. In fact, the higher the supply-voltage, the wider is that depletion zone. But electrons easily flow across it because they're being dumped on the wrong side! They see the wide empty zone as a vacuum, and easily cross it, driven by the strong e-fields in that insulator region. The wide BC junction acts a lot like the vacuum in a vacuum tube; it's insulating unless an electron cloud is supplied.
+wbeaty There is no misconception other than to say that in the absence of voltage there is an absence of current. There is also a book written by Bill Shockley who was probably a lot smarter than Horowitz and Hill put together. I should probably say that either Horowitz or Hill individually is a lot smarter than I, but we have to pick our gurus based on something.
+Richard Gray Of course there's a misconception. This error is exposed in any engineering classroom, especially in the semiconductor physics classes. The error isn't only debunked in AOA book, but everywhere. AOA is just an easily-recognizable example. The above video about BJT operation is oversimplified and wrong, using concepts typically aimed at low-level techs who don't need to do actual BJT designs. If you have no desire to understand the silicon itself, a wrong explanation won't hurt you. But the wrong explanation isn't necessary, since this "analog engineers' secret" isn't that complicated. But it does require that we confront and defeat the wrong concepts we've been taught. Many people won't do that ever. They prefer to believe that grade-school textbooks tell the truth, just like George Washington chopping down the cherry tree, and heroic Columbus who would never think of murdering or enslaving the natives.
So, what's the "Lies to Children" part of transistor explanation?
It's the mistaken idea that base current Ib can control collector current Ic.
To understand transistors' internal function, we must note that the base current has *no direct effect* on collector current. One current cannot affect another. Instead, the entire base circuit sets the value for base voltage Vbe (via the Shockley equation of course.) Then the Vbe potential-barrier determines both currents: Ib and Ic.
We can view this as Ib affects Vbe which then affects Ic ...and then we can go further and form a simplified 'black box', where Ib apparently determines Ic directly. But, if we open the hood and look inside, we find that BJTs are voltage-input devices, transconductance devices same as FETs, where the ruling equation is Ie=Is*e^Vbe/nkt -Is. This isn't that complicated! It's just transconductance: volts in and current out. Same as FETs and vacuum tubes. But we do need to have high-school algebra, so we're not scared off by nasty math like the diode exponential equation. And we must face the terrible horrible fact that Vbe is not actually fixed at 0.7v, and it never was. (Oh no!)
:)
All of BJT-engineering is based on this Shockley equation, the Ebers-Moll version, where base voltage determines Ie and Ic. It's why BJT op-amps have voltage input rather than Ib current input. In op amps, the differential-pair front end is a voltage-input transconductance circuit. (For those who believe in BJT current-input, the long-tailed pair circuit remains a deep and confounding mystery!) The breakthrough to understanding op-amp internals is easy: BJTs are voltage input animals, and your earlier teachers were wrong about the nature of hfe. Also, base-voltage is how current-mirrors work, and half the stuff inside any analog IC is the current-mirrors replacing the large resistors. Try explaining current mirrors or Cascode circuit based on hfe, where Vbe is fixed. Not possible.
Of course it's fine to use Ic=hfe*Ib in many situations. It's an extremely useful simplified rule of thumb, like Ohm's law.
Just don't try to use it to explain the internal physics of components, or everything gets loopy and distorted.
Yes, Shockley himself was beating the drum for "BJTs are current input." He was wrong, but had VERY good reason. His statement appears to be Bell Tel business-hype, done to make certain that USPTO wouldn't reject BJT patent applications, since voltage-input Lilienfeld transistors had already been patented twenty years earlier. Bell Labs had to distance themselves somehow from existing FETs. A good way to do this is to pretend that BJTs are current-input while FETs are voltage input. But it's not honest science (though it may be honest cutthroat business practice.) BJTs use voltage-input and use the (ahem!) Shockley Equation. Shockley worked out the whole semiconductor theory behind them. So, why would he claim that BJTs are current-input when he very well knew that they weren't? If he hadn't, there might not be any Bell Tel transistors; no patent, no profit, no aerospace contracts. Yet his small businessmans-lie is confusing-the-noobs even today. They just have to take some college undergrad courses to get the "hfe stuff" beaten out of them, and learn to slap on that Vbe Shockley equation just as easily as using Ohm's law.
+wbeaty Puhleeze. There is nothing wrong-headed about modeling a bipolar transistor using collector current as a function of base current. But, if you KNOW better than that, then I'm happy for you.
+Richard Gray Yes, that's a lot like modeling diodes as having fixed 0.7V voltage: often useful, even though certain designs would fail. And of course it tells us little about how diodes work inside.
The "current amplifier" model of transistors is fine as long as we know that it's just an ultra-simplified black-box model. Major trouble arises whenever people think it's really true, and then they try to base designs on it. The designs don't work (their resistors have to be hand-adjusted for each transistor used, and temperature effects are enormous, requiring thermistor compensation circuits.)
Also, classroom trouble crops up when we try to explain such things as Op-amp basics. The op-amp diff-input front-end relies upon base voltage signals, not on hfe, and it cannot be explained in terms of current-amplifier transistors.
---
I encountered this problem myself, on a very first professional analog design for an industrial opto-sensor. I was forced to abandon the current-based "hfe-think"; and instead spreadsheeted everything as voltage-input (transconductance) circuits where hfe is ignored. Worked fine. That sensor design is in coke machines everywhere.
Win Hill, one of the authors of "Art of Electronics" tells exactly the same story here: cr4.globalspec.com/comment/720374/Re-Voltage-vs-Current Before he could succeed at circuit design, first a wise old engineer had to take him aside and teach voltage-centric BJT philosophy, as opposed to the "current amplifier" stuff he'd learned in early schooling.
So, instead of first being taught that BJTs use current input, why don't we just do an end-run instead? Never learn hfe stuff at all, but directly jump into teaching that BJTs are voltage-input devices like FETs? After all, that's what they really are. But then we'll have to face the fact that our earliest teachers were lying when they taught us that George Washington chopped down a cherry tree, or that Columbus was a saintlike hero, or that BJT transistors are current amplifiers. Or that William Schockley cannot tell a lie! :)
+wbeaty Well, I knew as a second-grader that it was bullshit when my teacher told us that George Washington never told a lie or as a seventh-grader when we were told that Isaac Newton watched an apple fall and thus invented gravity. But, later, I never got that feeling about hfe being a useful device parameter.
hell yeah you explained it better...in fact better as my university professor :)))
one of them told us that the nm it the size of the transistor(capsule) not the distance between channels
Excellent Dave!, and a great followup from your last video on why you should learn electronics. Learning a lot and really enjoying it.
Tom
Why do we even use conventional current flow? It appears to only create more confusion.
ronettreker Because it makes more sense and also follows the the arrows in diode and transistor symbols.
From what I know those symbols were created because of conventional current flow. Anyway, nevermind that. I don't understand why does it make more sense... I'm really curious.
ronettreker Water runs downhill, from the higher up potential to the lower potential for example. Thing like that make conventional current more relate-able and more "obvious" that current flows from positive to negative. That's why they thought that was the case to begin with, it wasn't an arbitrary choice.
EEVblog Isn't the number of electrons in a medium that define it's potential? I thought that electrons flow from a medium wich contains more free electrons to a medium which contain less, in order to achieve equilibrium. I thought the reason why the higher potential medium is negative is because of the higher number of negatively charged electrons. If so, then the negatively charged medium is the one with higher potential, not the positively charged one. Did I got it right?
ronettreker i think you may be missing the point I was trying to make. I was trying to show how (unless you know the details) it's more obvious to the lay person that something (current) would flow from something higher (potential) to lower (potential).
Thanks for the video, but there is one misunderstanding. 15:50. The depletion region is formed by the negative ions in the p-type/substrate side and the positive ions in the n-type (source) side, not electrons and holes like what you mentioned. The negative ions (acceptors) are created in the p-type/substrate side due to the gain of electrons diffused from n-type, whereas the positive ions (donors) are created in the n-type/source side due to the loss of the electrons which diffuses to the p-type/substrate side. Hope you can add notes there (15:50) to not let people misunderstand this. Thanks.
Really good explanation. I love this channel! A lot of useful stuff. Thank you ,sir !