How Diodes Work - The Learning Circuit
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- เผยแพร่เมื่อ 25 ก.ย. 2018
- Karen goes over how diodes work and shows you what happens when you hook it up to a power supply in a circuit. Want to ask Karen a question and know you'll get an answer - ask on element14: bit.ly/2IdXrpI
There's an eBook version of this content available for free download on element14: bit.ly/3oBCg5O
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Diodes have two axial leads coming out of both ends with a stripe in the middle to indicate which end is the cathode, or the negative end. A diode is an electrical component that allows current to flow in one direction but not the other. Diodes are made with a semiconductor material, mostly silicon but sometimes other materials such as germanium, selenium, or gallium arsenide.
Semiconductors typically have four valence electrons in their outer shell. Silicon, being a semiconductor, also has four outer valence electrons. This outer shell can hold up to eight electrons. Electrons are most stable when their outer valence shell has eight electrons, a rule known as the octet rule. Each silicon atom shares an electron to its neighboring silicon atom in order to satisfy the octet rule. When silicon atoms form covalent bonds they crystallize into a very strong structure known as a crystal or a lattice.
In the P-type region silicon is doped with boron or gallium. Boron and Silicon have only three outer electrons. When mixed to a silicon lattice, they form “holes” in the crystal structure electron has nothing to bond to. The absence of electrons gives it a positive charge. In the N-type region silicon is doped with antimony, phosphorus, or arsenic. The fifth electron becomes a free electron. It is free to go wherever the current takes it. These free electrons are negative charge carriers.
The point where the N-Region and the P-Region meet is called the PN Junction. Near the junction the positive charges and the negative charges, having opposing charges are drawn to each other like magnets. The free electrons in the N-type region migrate over and fill the holes in the P-type region. Because of the charged particles moving around, the area near the junction in the P-type region becomes slightly negatively charged while the area near the junction in the N-type region becomes slightly positively charged. This area is known as the depletion zone. Eventually, the depletion zone becomes charged enough to stop electron migration. In a silicon diode this happens at around .7 Volts. - วิทยาศาสตร์และเทคโนโลยี
for the people who don't understand, write down little short notes on the information said in the video . it is a great way to understand and process the facts. thank you for the really amazing video.
The concept of the diffusion potential barrier at the junction is not explained correctly, although the rest of the video is well narrated. The positive charges in the N region depletion zone do not repel the negative charges in the N zone (4:45). Positive charges do not repel negative charges! It is similarly incorrect as stated for the P region (4:52). Rather, the developed potential across the junction becomes a barrier to further charge movement ACROSS the junction, in effect, sending charge backward -- and at a potential of 0.7 volts the charge movement in both directions across the junction becomes equal and opposite. I would have a look at some other videos on semiconductor diodes which better explain this concept.
Wow! This was really informative. I've been in electronics hobbyist for years I never really dug into why diodes work, I just know that they do. Thanks for the information
Thanks for another great learning circuit episode. It's always nice to learn the science behind how various electrical components work. And I think the humorous presentation helps keep things interesting. Keep up the great work.
Great interactive video! And thanks for discussing the proper “Electron Flow”, so students will not get confused. You rock!
I was literally crying , i would fail this semester ,then i found this video .
this is surely God send am so happy you made it so simple for me to understand.TQ
Excellent description and visuals for the interactions of N, P and depletion zones. This, and describing in terms of electron flow has been a massive help with understanding diodes and transistors.
Best tutorial I have found. Thank you!
You're a lovely demonstrater with a very magnetic personality! Thank you so much for your contributions!
Great teaching as always! Nice work Karen and element14!
I am an electrical engineer. This is the first time i am getting an understanding how a diode works. Moving on to the bipolar junction videos you have posted. Thank you...
It was good up to the point where opposite charges 'repelled each other'
lol I was like "wtf did she just say?"
Aren’t the n and p regions also illustrated backwards? P is supposed to be anode…
Good work and very well explained 👍
While searching for a tutorial for a new co-worker and stumbled across this. Great explanation and fantastic depletion zone section! One request: the electronics industry is shifting away from through hole so showing some surface mount parts during part choice section would be great.
The best explanation I have ever heard!!
Amazing explaination! Thank you!
Nice! Thank you for this video.
Karen, thanks for the selfie at the Wisconsin Maker Faire Saturday. I almost didn't recognize you without your gloves. Luv the shows too. - Sid
Great video!
Got all my doubts cleared
Thank you very much ! 😃
Well presented
Terrific keep it up 👍.....Thanks Karen.
Lovely video. Also, I am intrigued by that Art of Resistors video behind you.
Thanks for the good explanation!
Wonderfull class. Congratulations!
Karen is Great!
Great at being BAD, you forgot the last part.
This is the clearest explanation of diodes I’ve ever seen
Thank you so much for your help
best 101 a diode yet, nice work
crisp and clear!!
Great Video. I would love to see same for Transistor and Thyristor. ❤🤗🔥🇮🇳
Thank you for the information! It may be useful to point out that "outer valence shell" does not imply that there are any inner valence shells.
Love the "two friends mad at each other" analogy.... Thanx!
I'm from🇹🇿🇹🇿🇹🇿🇹🇿🇹🇿🇹🇿some where in Africa and I do appreciate what you do
very instructive thank you
Finally, an explanation I understand!
help!! help!!! help!!!! 4:51 Why does the positive charge in its depletion zone repel the negative charges in the region? Should not the negative charges in the region be absorbed by the positive Charge?????????? I have watched mang videos about this theme!!! I just don"t understand this point!!!!! Can you explain this once??? thank you very much!
This makes sense! Thank you!
Thanks to nice tutorial godbless.
I enjoyed your video, very informative. Although your video shows "electron flow", I can see how "conventional current " might be also used to show the current flow since the schematic arrow (diodes and transistors) points in the same direction. I can also see how " tech people " might be passionate on which is more correct.
Best teacher💯
nice explanation
Great teacher....
She is the only few Karen I would want to learn from.
Finally someone who talks plainly about a diode. Thanks.
awesome teacher
many thanks! 👏🌼
@ 4:20 you say the p and n regions become slightly pos and neg charged. Why and How? If the extra electrons in the P region left to fill holes in the N region and visa versa, then didn't those atoms just become neutral again with 4 valance electrons like the original silicone atoms? Sorry, this is the part I never understand.
A Karen that we can all appreciate :)
I AM A TEACHER BUT I LOVE THE WAY YOU TEACH
I have always been curios about this
GREAT JOB
Great teacher
At 7.10 Are you sure you didn't mix up + and - in the depletion zone?
You refer to "outer valence shell electrons" in the video. Wouldn't you consider that terminology redundant as the valence electrons by definition occupy the outer orbital in Bohr model? In other words, isn't "valence electron" sufficient to describe what we're talking about in semiconductor physics?
Thanks Karen!
Another great lesson from TLC! Diodes and transistors are cool because they are driven by the interactions of the physical properties of the materials from which they're constructed. Hooray physics!
Also, if you want to see a fun application of diodes in a circuit, check out the DIY Geiger Counter video on element14 Presents!
You are very good teacher
Hi KC, thanks for the best graphics and explaination of the rectifier diode I've seen yet! And ya gots personality and humor ta boot.😊
Your room is set up real nice orderly. I can see your into arduino and robots too. I bet your students love you!! I'm still blown away by the graphics!
I learned a lot of this stuff starting in 1979, went a Technical college in 1986 and was taught by a few military instructors. Now I'm an instructor and love to refresh my memory and use your material to teach with. So much faster!
If you have the time, could you make a short video on electron verses convetional flow? The students always get confused Thanks!
I truly believe the smart tech, engineer, or maintenance person should learn both ways to be real good and be fluent in each others languages rather than fight it like so many of the Dems and Repubs do politically, and our world would be so much more peaceful and by teaming up and getting a lot more done.
Thanks again!
at 4:20 the positive atoms don't move. They are bound inside the latice. Only the negative free electrons move.
thank you so much
This is a very good video.
love your energy!!! jajaja
Since diodes lower voltage - would they make better voltage dividers than resistors?
How come you have plus and minus on your diagram when both electrodes are grounded?
I do not understand why this video shows electrons bonding to each other (how it was drawn on the whiteboard) or what they are saying about the “depletion zone gains enough negative charges to repel the positive charges” as opposite charges attract eachother. Please explain
thanks teacher
I like your program very much and like you too.
When junction was formed and positive charges were crossing the junction so why they stopped?
Why don't positive charges go to join the next negative charges in the remaining part of the diode?
the semiconductor nuclei and the doping element's nuclei, are forming a lattice. Most of their electrons are trapped just fine in their valence shells. We're only getting a flow of excess electrons rushing through.
4:40 youre saying opposites now repell? Whats going on?
exactly. I am wondering the same. The diagram changes completely at 5:40 XD.
She was showing what happens when a diode is connected backwards, the reason current only flows one way through a diode. What happens when you connect it backwards? The N&P type separate further, that's the repelling you see. Connected backward so what's happening is right, negative side is attracted to the anode(pos) and positive attracted to the cathode(neg). it's repelling because it's backwards. she then installs it correctly, showing the flow.....
Eventually, the electrons in the P part of the depletion region create enough of a negative charge to repel any additional electrons from crossing over.
There’s enough negative charge in the depletion zone to repel what’s left in the N region, and enough positive charge in the depletion zone to repel what’s left in the p region.
That is how it works in current , at first negative is weak and it needs positive ,but when there are lot of negatives it feels safe and do not need positive and repel the , it is like a person needs another special person to feel safe and happy but when that person gets some friends he feel safe and do not need that special person
Thanks!
Nice 👍
I love your Teeshirt, Karen!!!
7:57 - How do you have a >0.7 voltage difference across the diode when both ends are connected to a common ground?
Was wondering the same thing.
4:13 i am confused. How are the holes moving? I thought the holes were not free to move.
Hay un error en la animación de la polarización inversa del diodo. La zona de deplexion en la zona N debe tener iones positivos y en la zona P debe tener iones negativos.
very nice
One use is the commutating, or freewheel diode. They’re placed in parallel with coils so as to provide a path for current created by collapsing magnetic fields. Typically used with relays, contactors etc.
how do electrons bond when like charges repel ? is it spin or is it a covalent bond you mean where the valance orbital is sharing electrons ? , not sure what you are saying
If you're talking about when I was drawing on the dry erase board, it's not that they're bonding. The outer valence shell of those atoms can hold 8 electrons. So each atom has 4 of its own electrons and "borrows" 4 more to fill its outer shell, 1 electron each from 4 other atoms. The electrons aren't necessarily bonded, but they are shared by two atoms, which helps bond those atoms together. Does that help?
Wow thanks for reply. Yes that when I was talking about, and your reply makes it clearer now.
How did you know exactly where I was talking about... I'm flipping out. So cool....... 😀
Wonderful explanation just like you rose
I'm struggling to grasp this. why does negative repel positive?
That is how it works in current , at first negative is weak and it needs positive ,but when there are lot of negatives it feels safe and do not need positive and repel the , it is like a person needs another special person to feel safe and happy but when that person gets some friends he feel safe and do not need that special person
Thanks to Karen for bringing the straight doping.
Karen ,if doping of pure silicon will cause reduction in the physical strength of silicon, especically in p side.beacuse p side have holes.will it create weakness.please reply. Iam doing a resarch in electrical field so, please give proper answer . Its a request. Iam a engineering student.age 22
Can you also explain how PIN diode work?
There is another correction besides "opposite charges repel", while performing reverse bias anode is depicted as +ve terminal later on while performing forward bias anode is depicted as -ve terminal.
From a science teacher perspective: great video, great explanation, great graphics at the beginning, but this video becomes confusing after about 4 minutes.
For instance, at around 4:45, the following sentence does not make sense for students, as they learn that (-) and (+) charges actually attract each other: "N type side gains enough positive charge in its depletion zone to repel the negative charge in the region".
Before that, the graphics are showing that (+) charges are moving from the P region to the N region, which also fosters misconceptions in students. It's the (-) electrons that move from the N region to the P region, leaving behind (+) charged ions. That means that (-) charges build up on the P side, which then starts to repel more "incoming" (-) electrons trying to hop over to the P region from the N region. At the same time, the (+) charged ions (the ones that are left behind at the N side, from the first few electrons that hopped from N to P), are now more strongly attracting any (-) electrons that are also trying to hop from N to P, making that more difficult. So, the (+) charges don't move, rather, it's the movement of (-) electrons that leaves behind (+) charges. The subsequent attraction between (+) ions and leftover (-) electrons in the N region on the one hand, and the built up of (-) electrons repelling each other in the P region on the other hand, is what prevents all the "holes" in P from being filled with "leftover" electrons from N.
So, overall great attempt, but not something that I'd comfortably use in the classroom.
Thankyouthankyothankyou, Ian, for this explanation. You're awesome. I watched this video over and over again without gaining any understanding about what happens at the depletion layer. None of what Karen said made any sense to me. Honestly, the more I watched, the more confused I got. Your explanation answered all my questions, and is the best I've read or heard anywhere. I've copied and pasted it into my notebook. Thank you again.
The depletion zone of the n side if the junction should be positive charge but you label as negative.
Unless you mean the n material being a source of negative mobile charge carriers. But after they diffuse to the p doped material the n type material near the junction takes on a positive charge.
Similarly on the p side of the zone a negative charge develops locally.
The crystal as a whole is still electrostatically neutral with local effects isolated to the junction.
The charges are not homogeneously distributed thru out the crystal but rather accumulate in equal amounts at the p n junction and so cancel out so as the crystal to remain in electrostatic equilibrium as a whole.
That's my understanding at least.
thanks 😊 😇
Did you heard that fart .....4:48
I am sure you didn't...🤣🤣🤣
You are legend.
I saw it different way. When positive terminal is attached to negative n-region of diode, it suck the electrons out(or it's trying to take electrons), that causes the free electrons to be depleted in the n region becoming an insulator. Because electricity moves by free electrons. The p region connected to negative, causes the electrons to neutralize the positive region turning it into an insulator. So the diode becomes an insulator in both p and n location with no free electrons for electricity to move through the diode when the terminals are attached incorrectly.
It doesn’t damage or destroy the diode if it goes in breakdown, it could destroy the diode as all components have limitations to what currents it can handle. But it has nothing to do with being in a breakdown state. This is a nice video.
you'r great....
best video
very very easy method
What about zener diodes?
@4:49, less the very small leakage current, while in reverse polarity.
How does capasetor work
Karen, how about a full bridge rectifier circuit of diodes?
Wow a intelligent woman with a sense of humour.
Hello sister from UK, Wales. 🙄
Ugh, what a cool teacher.