Forward biasing a PN junction | Class 12 (India) | Physics | Khan Academy

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In this video, we will attach metallic contacts at the end of the PN and provide a voltage across it. When we connect P side to Positive and N side to negative, we call it forward biasing.
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Class 12 Semiconductors: We cannot imagine our life without computers today. But what makes a computer tick? What's making this technology grow at such an exponential rate? It's all due to semiconductors. As unbelievable as that might sound, altering the properties of semiconductors allows us to build these computers. In this topic, we will explore the world of semiconductors. It's a journey from what semiconductors are all the way to creating building blocks of these computers.
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16 окт 2024

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Комментарии : 116

@nagarmalsharma9992 5 лет назад

The best explanation of semiconductors on the whole internet, never understood this concept, but you made it really intuitive, thanks!

@proudnepali8388 3 года назад

Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???

@Hari-wi7sr 3 года назад

@@proudnepali8388 yeah ur right. ig we are assuming the vacant spaces as holes.

@jackeinstein2184 Год назад

@@proudnepali8388a as Xa rqxw

@VenkatasaitejeshAmbati 8 месяцев назад

@@proudnepali8388 bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes . Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.

@Funchoz_learn 4 года назад

Superb video quality ... This man has put his heart and soul to it

@cradleblaze8798 3 года назад

Damn sir .... What a detailed analysis of semiconductor .....Helps for jee preparation !!!!!

@osamazahid715 6 лет назад

your lecture Answered my lot misconception, you rock the stage!

@ishitachadha1786 2 года назад

You are by far the best animator. I can actually believe and visualize what is written in the book because of you. Please keep making many more videos:) You really helped me out!

@anushkavora7815 8 месяцев назад

one of the best videos i have ever seen out there. so simply explained with the right gear, everything is perfect about it and super easy to understand

@prateeksharma6756 2 года назад

Sir why are they not recombining and increasing the depletion region when you are connecting it to a battery.

@seemabharti1757 6 месяцев назад

I have a question If in forward biasing the electrons flow from n type to p type region Then shouldn't the depletion region increase. And electron may recombine again with holes, like they did when the depletion region was initially formed

@singam5084 15 дней назад

There is constant potential is applied right then there is chance of recombination as the electrons were keep on feeding by potential thus no recombination I think in this way😊

@nehapal6888 3 года назад

Made me speechless... Amazing Wish all teachers should like you

@ishakatira8650 2 года назад

Doesn't the rate of recombination now increase as more holes and electrons are now moving?

@killiyaswanthkumar9429 Год назад

sir, your way of teaching is so great,pls clarify my doubt/ when ext electric field is applied from p to n type then diffusion current increases,that doesnt destroy the charge carriers and increases internal electric field from n to p type which further increses the barrier width?

@SIMRAN-kz5dw 2 года назад

In addition to ur extraordinary teaching of physics.....ur vocabulary is excellent as well. Like "All hell breaks loose " "Diffusion current sky rocket's " Plz teach us English too .....ur amazing sir

@harshsingh-h3s 19 дней назад

6 YEARS STILL THE BEST VIDEO EVER

@mariaa6181 7 месяцев назад

Great! It would be also nice to see band diagrams associated to this pictures in the video. Like the ones in previous videos.

@muditagarwal1781 2 года назад

The most productive 6 mins of my day today!

@PoojaShankar-p3d 9 месяцев назад

Simply brilliant sir❤

@srilakshmidevulapalli6999 8 месяцев назад

Thanks a million !!

@VenkatasaitejeshAmbati 8 месяцев назад

bro actually holes are vacant spaces as you said only the electrons will be crossing the barrier but not the holes . Holes in p type are present in the valence band of p type wheras electrons in n type are in conduction band so to reach the valence band of p type they have to first reach conduction band of p type which has very few electrons(which are minority carriers of p type) and then loose energy to goto valence band to fill the vacant spaces.

@yashboss9593 2 года назад

Explanation: top notch Time: 👍

@suchitrasridhar5313 5 лет назад

This is a great video. I just wish there were more Khan Academy videos aligned to CBSE curriculum.

@KhanAcademyIndiaEnglish 5 лет назад

I feel you. We are working on it for class 10th currently.

@tasneem6427 3 года назад

They are kind of connected to the cbse curriculum I guess. I’m a cbse student and many of the topics they have are a part of cbse curriculum

@prakashchandraaman7885 2 года назад

Great work khan academy though i am preparing for GATE i had confusion before seeing your videos and nobody else other than you explained it in crisp and crystal clear way ....keep this good work continued

@harshchoudhary3redrose753 7 месяцев назад

I wonder which app he uses for the videos...amazing

@Pursuit-of-lyf 2 года назад

This video is great to conceptualise the PN junction mechanism.. i have just one doubt.. plz clarify it.. as u earlier said in previous videos, diffusion would expose the charged ions B- and P+ so with time drift motion increases due to minority charge carriers due to depletion region?? Isn't it?? Or is it just about the dominating factor? That here depletion region goes down inturn increasing diffusion current rather than contributing to drift motion?

@MuktarHusseinG 4 месяца назад

It is very clear explanation

@lollopes100 4 года назад

Why is the diffusion current increasing when you apply a forward bias ? Drift currents means that the motion of charges is due to an electric field while Diffusion is caused by difference in concentration. When you apply a forward bias you create an applied electric field across the junction that will make the carries DRIFT to the opposite side not DIFFUSE.

@codeminatiinterviewcode6459 3 года назад

You can think in this way that, When we are appling the Forward biasing then the majority charge carriers (Let say holes of the P Region ) are facing the repulsion from the holes that are coming from the battery (As it is Forward Biased), Knowing the fact that battery also emitts nothing but the free charge carriers. So due to this majority carriers start pushing in the forward direction and hence the current due to majority charge carriers in forward direction increases (So called as diffusion current). Drift current is due to minority charge carriers (These carriers are the ones that are present before the doping when the semiconductor was so called INTRINSIC Semiconductor, In which both the electrons and holes are present in equal concentration and the doping came which increased the concentration of one type of charge carrier and made another one a minority charge carrier.), So if we are appling forward biased then these will oppose but their oppose is very little as compared to majority charge carriers (As their concentration is also low). Hope this helps. :)

@abdullahbnl6979 Год назад

Your notes available? If available where to find them...reallly besttt teacher ever now a month left to my exams, no time to write lecutres as I've 3 days to prepare I wish O had find them before😢😢😢😢

@sadiaafrin4208 Год назад

Best bestttttt🔥🔥🔥🔥🔥💞💞💞💞💞💞 I finished my 12th class with dissatisfaction of this chapter,bcz it’s concept wasn’t clear for me. Now after long time im seeing this and feeling so happy and having content, i cant describe 💜

@nitink9879 3 года назад

5:58. Sir, is the cut in voltage at forward biasing is equal to the barrier potential of the semiconductor?

@khushi11147 11 месяцев назад

But if the diffusion current is increasing, how is the depletion layer decreasing in size? Won't the rate of recombination increase with diffusion?

@charuprabha4534 3 года назад

Man u r really great pls keep uploading more vdos on physics ;)

@vishank7 4 года назад

Hello sir, what happens to the electrons after they migrate towards the P side? Do they recombine with the holes, and does the pair get destroyed? If so, wont amount of charge carriers go down with time? Thanks already!

@KhanAcademyIndiaEnglish 4 года назад

Great question, I guess this is covered in great detail in the next video titled "Forward & reverse current mechanisms"

@vishank7 4 года назад

@@KhanAcademyIndiaEnglish Khan Academy India - English Thank you for replying sir! I just watched that video, and it was truly helpful. Really glad that I understand how it works now! Just one more doubt sir, Given enough time, will the diode run out of majority free charges in reverse bias as the depletion region keeps on growing?

@proudnepali8388 3 года назад

Please help me‼️‼️, how can holes travel to N region , they are just the vacant place where electrons lack right ???

@ayushdash6858 2 года назад

Simply Brilliant 👏 👌

@ojussinghal2501 5 лет назад

Great fun, well explained.

@caghey 7 месяцев назад

that was too good omg

@nitink9879 3 года назад

Sir, I have a confusion in this concept for many years. Could you please solve my doubt ? 4:31 If the barrier voltage is 0.7 volts and you are applying 0.2 volts in forward bias, there is still 0.7 - 0.2 = 0.5 volts of barrier potential. Then how does the current flow ?

@KermitB_1815 2 года назад

I am not sure if i understood it right but i think when the value was 0.7 only a few of em could go across the depletion region but when it was reduced to 0.5 and also at the same time made the region smaller, it basically made it possible for some more of the holes (which could've crossed with lesser energy) to go accross the depletion region and vice versa for the electrons. Hence as it isn't under equilibrium anymore, current flows.

@ananyajaiswal5928 Год назад

Such a great explanation.

@DisiCoco-nm2gw 16 дней назад

Thanksss 😊😊

@nitishpatil953 7 месяцев назад

If the electrons are moving from battery to n region and filling the holes in p type region then why the flow of electrons/electricity is opposite in simulation?

@mibrahim4245 2 года назад

regardless of this awesome video .. I AM SUPER CURIOIS TO KNOW, WHAT IS THE BRUSH TYPE AND SIZE THAT YOU USE IN SKETCHBOOK!! .. please let me know

@shrishmagar375 4 года назад

what software are you using?

@lublymoarmy 9 месяцев назад

I should ask this cuz this question is really irritating me. If the diffusion increases in the forward-biased PN junction shouldn't there be more exposed ions and shouldn't the width of the depletion region increase?

@betulteymur9217 3 года назад

Can you also please explain heterojunction energy band diagrams with the same simple explanations?

@saakshhhiiii 2 года назад

amazingly explained!

@niranjan7457 3 года назад

Sir while Forward Biasing a PN Junction, there will be current flowing in both directions, right? Because both diffusion (major) and drift (minor) are happening. So there will be a tiny current flowing from N to P. So we can't use this Forward Biased PN Junction in daily life (as the main goal is to allow current to flow only in one direction)

@KhanAcademyIndiaEnglish 3 года назад

In forward bias, the diffusion current is orders of magnitude larger than drift, so there is a high current from P to N. In reverse bias, there is a very tiny drift current from N to P. In most applications this is negligible Thus the diode acts as a one-way switch, conducts in the forward bias, but doesn't conduct (negligible conduction) in the reverse bias. Hope this clarifies your doubt.

@tamratchurko1077 2 года назад

Thank you a lot !!!!

@meleyere7519 Год назад

Is it conventional current?

@Skz716 Год назад

If you want understanding.....physics wallah If you want depth and clear concept....Khan academy

@lakshminandhana2058 2 года назад

Thank you sir

@sudhanshu149 6 лет назад

Awesome

@rijuwanahaque8054 7 месяцев назад

Q. True or False: In a pn junction diod without any external potential source, the diffusion current and drift current are caused at the junction by- 1. Majority carriers for diffusion current 2. Minority carriers for drift current 3. No current at the junction

@luscinia_74 5 лет назад

If diffusion increases won't all the holes and electrons recombine and get destroyed....then there will be no more particles to conduct.??

@KhanAcademyIndiaEnglish 5 лет назад

Good question. Let's think about electrons. Towards N side terminals there are loads of free electrons (as most holes don't make it there). Think of this terminal as the source of electrons. Now as these electrons diffuse into P side they keep recombining. The lost electrons are replenished from that 'source'. Okay so won't that 'source' eventually run out of electrons? No. For every electron that moves out of it, it pulls an electron from the wire immediately next to it. That's how electrons move in the wire as well. Let me know if this helps.

@luscinia_74 5 лет назад

Oh......i get it now.....thanks a lot!!!

@nooreldali7432 5 лет назад

very nice and simple thank you

@sugam_24 3 года назад

This guy casted a magical spell on me cause I got this topic crystal clear. (Matter of shame:)👇👇👇👇👇 ( I learnt this in school with my teacher and even attended a video lecture for an hour on youtube but still I wasn't convinced.)

@proudnepali8388 3 года назад

Which school? Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???

@proudnepali8388 3 года назад

Bro I guess you r Nepali please help me if you have understood this

@vijayvijay906 4 года назад

Electron move from n type to p type for diffuse of their Barrier and back to the battery

@mahmouddesokey3818 5 лет назад

Perfect 👏👏

@MartinPurathur 4 года назад

Thanks

@CGuevara00 3 года назад

¡Thank you!

@proudnepali8388 3 года назад

Please help me, how can holes travel to N region , they are just the vacant place where electrons lack right ???

@abhinavarvind2638 3 года назад

The battery applies an electric field from positive to negative initially since diode is forward biased consider holes as +ve charge carriers for simplification

@jy_decipherer_5515 3 года назад

Hi! I just want to ask why the voltages in the neutral zones don't change when a forward bias is applied? Since we know that when voltage is applied to any component, there will be an electric field inside it which points from positive to negative, and since the diode originally has no electric field in its neutral zone to cancel it, shouldn't there be a voltage in the neutral zones? Is there some kind of mechanism that counteracts this?

@KhanAcademyIndiaEnglish 3 года назад

That's a great question. We are doing a lot of assumptions here, and one of them is the negligible resistance in the neutral regions. This is similar to how we neglect the resistance in wires and assume no electric field there!

@proudnepali8388 3 года назад

@@KhanAcademyIndiaEnglish Please help me‼️‼️‼️ please , how can holes travel to N region , they are just the vacant place where electrons lack right ???

@subashkc7674 3 года назад

@@proudnepali8388 Hole are the vacant space. Since the negative terminal of the battery is connected with n type semiconductor where electron are the majority charge carrier. And the positive terminal of the battery is connected with P type semiconductor where the hole are the majority charge carrier. Due to the repulsion between negative terminal of the battery and free electron as well as the repulsion between positive terminal of the battery and hole the depletion layer width decreases. So that the some energetic free electron migrates from n type semiconductor to P type semiconductor due to decrease in depletion layer(resistance decreases). Before migration in the n-type semiconductor there was neutral condition but after the Migration of some energetic electron there are generated some hole in the n type semiconducyor. So due to migration of free e there is some hole are generated. That we call migration of hole .

@jy_decipherer_5515 2 года назад

@@KhanAcademyIndiaEnglish Thanks for the response! I think that clears things up for me then

@Kyle_da_athlete 5 лет назад

Great video

@vijayvijay906 4 года назад

The current in diode back to battery

@shalinirameshbabucool 5 лет назад

How does increase in diffusion current decrease the depletion layer? It doesn't make any sense coz diffusion caused depletion layer.. plz do reply this question..

@KhanAcademyIndiaEnglish 5 лет назад

The depletion layer decreases due to the external power voltage supplied. This inturn increases diffusion because the depletion region was acting as a barrier for diffusion.

@reetichauhan355 4 года назад

Khan Academy India - English Why is it not that the diffusion current increases and so the depletion layer again becomes wider due to it?

@b.srinivas9567 3 года назад

If holes move towards electrons then why recombination not occurs??

@aswin8063 3 года назад

I think recombination occurs ..

@sircliff323 5 лет назад

holes move?

@ZainAli-qy1jd 4 года назад

Holes aren't any thing the are just the absence of elctrons

@girishdeshpande6843 4 года назад

Why don’t the boron and phosphorus atoms just combine chemically and form boron phosphide instead of existing as separate layers just beside each other?? In an atom, the constant motion of electrons and the presence of neutrons altogether prevents the electrons from just collapsing into the positively charged nucleus, what stops boron and phosphorus from chemically combining here??

@surmanikonsam3793 3 года назад

Am I seeing things or the arrow got brighter when increased voltage 😶

@Parapresdokian Год назад

No, you're wrong. This guy could even make ToyStory using this software.

@hassanjaved6485 5 лет назад

All the concepts you gave upto this point were great but this video has pretty low standard as far as concept is concerned... you should have talked about flow of electrons rather than saying holes are flowing and should have talked about conventional and electron current

@KhanAcademyIndiaEnglish 5 лет назад

There are two types of electrons. Free electrons that flow freely, and valence electrons (which are covalently bonded) which move from one 'hole' to another. These two motions are pretty independent of each other. The free electrons literally move over some distance. But the valence electrons just jump to a neighbouring hole, virtually moving the hole in the opposite direction. Then the next neighbour will jump in and then the hole again moves (virtually). So you see these valence electrons are not really moving from one place to another (just jump to their neighbouring space and sit there). Hence it makes it both easier mathematically and intuitively to imagine that these 'holes' are moving. This is why we treat holes as a separate individual particle and consider it's motion in the valence energy region (just like how free electrons move in the conduction band region). If you need more details on this, they are explained in previous videos, do check out the playlist. Hopefully, it would help.

@reetichauhan355 4 года назад

Khan Academy India - English that’s an amazing explanation to distinguish between how we Conceptualise things for ease vs how it actually is. 👏👏👏

@gold8780 5 лет назад

Your explanation is good but please stop with the fake accent sir. It's seriously irritating.

@gerrycalhoun9827 5 лет назад

How on earth is that a fake accent?

@gold8780 5 лет назад

You can _probably_ notice it if you watch other videos of the same lecturer

@gerrycalhoun9827 5 лет назад

@@gold8780 yeah I have watched videos with the same lecturer. It's just an Indian accent, how is that fake?

@gold8780 5 лет назад

@@gerrycalhoun9827 I guess it isn't an Indian accent that's why?

@gerrycalhoun9827 5 лет назад

@@gold8780 The guy (Mahesh Shanoy) is an indian. From India. It's not fake accent, it's an indian accent. Because he's an indian, from India. Plus you're on a channel called Khan Academy India and you're complaining about an indian accent?