How Diodes Work - The Learning Circuit

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.

[lovinmunasinghe]

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.

[protonman]

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.

[fezickthebig]

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

[brandtharen]

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.

[wesleychiminya]

It was good up to the point where opposite charges 'repelled each other'

[dardale]

Great interactive video! And thanks for discussing the proper “Electron Flow”, so students will not get confused. You rock!

[iansmith]

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.

[Rei-mg]

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

[tribulationcoming]

Thanks, I'm and experimenter and look for results, but lately need to understand the diode. Very good and be safe.
Built one pulse motor that ran for two years and charged it's own battery. Took down all the video's which had been posted, thinking about putting them back up. Thanks again.

[k.m.parekh]

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...

[changarawemichael]

I'm from🇹🇿🇹🇿🇹🇿🇹🇿🇹🇿🇹🇿some where in Africa and I do appreciate what you do

[reccothomas]

You're a lovely demonstrater with a very magnetic personality! Thank you so much for your contributions!

[nicholasaikens]

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.

[Sidman]

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

[colza]

Best tutorial I have found. Thank you!

[BenjaminNelsonX]

Great teaching as always! Nice work Karen and element14!

[jmpattillo]

This is the clearest explanation of diodes I’ve ever seen

[feiwang]

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 I have watched mang videos about this theme!!! I just don"t understand this Can you explain this once??? thank you very much!

[curtpiazza]

Love the "two friends mad at each other" analogy.... Thanx!

[RohitChavanTM]

Great Video. I would love to see same for Transistor and Thyristor. ❤🤗🔥🇮🇳