Zener diode voltage regulator | Class 12 (India) | Physics | Khan Academy

In this video, let's explore how a Zener diode can be used to regulate voltage. We are going used it's reverse breakdown characteristics.
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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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Created by Mahesh Shenoy

[@alphamax157]

best video by far after scrounging over more than 20 videos on the topic.

[@beinghuman1036]

Me too

[@mohamedkalith7607]

Hello i have a doubt

[@BEC_VishvdeepSinhmar]

yaaaaa

[@divyanshkalra8587]

@@beinghuman1036 same here very good explanation

[@pradipbhandri]

This is the only video In entire KZbin to understand the pure concept of Use of Zener diode as voltage regulator very easily

[@moya9450]

Why we don't use zener diode in Series connection with the LED?

[@rayanjaved6264]

​@@moya9450because we're dumb

[@shreyakulkarni9240]

​@@moya9450 bcoz at breakdown voltage, current would increase massively, n LED will blow up

[@Parapresdokian]

7:12 I'm watching this at 2 AM, yet still I involuntarily laughs along with him and woke everyone wide. Your laughter is contagious dear human.

[@Mohanvenkat]

I have been using the help of Khan Academy for over 5 years and it's only getting better. Great video on the topic!

[@Shubham-rl7zw]

Thank you thank you so so much .. I was so much confused about that short circuit part ...best video on whole internet ♥️❤️😍

[@manohardivi2593]

Here I can feel the concept .... If I get teacher like him I get full marks...

[@GENESIS-zp4cy]

After watching 20+ videos... I found this.... Thank you very much sir..

[@RAHUL-jg6ss]

Best video on this topic in this ।।।great job guys !

[@zitscx886]

you are really underrated. Best teacher i hv met so far...

[@arunnithyaanandam3078]

So if the resistance of Rs can change according to the input voltage and y do we need a zener diode in the first place? Can't we just use the resistance to make sure only 2v enters the led bulb?

[@revitharevitha5356]

We could only make the voltage drop using resistor and the current increased due to increase in voltage flows across the zener diode and hence doesn't affect the LED light

[@alekhyaalekhya5912]

Really satisfied with this video.......no more exceptions this is the good lecture

[@runzit2007]

Lecture on Photo diode and LED plz

[@KhanAcademyIndiaEnglish]

When we made this project, we had a little time crunch, so we decided to skip those topics and focus more on transistors (which I personally believed was more challenging). We will come back to this once we reinitiate this project :)

[@sampritipatel8981]

At 2V , the zener diode acts as short circuit so no current should flow through LED. But it still glows. So is potential difference the only requirement?

[@KhanAcademyIndiaEnglish]

A current will flow through the LED. Usually, when we think of short circuits, we assume voltage across the ends of that wire is zero. (because V = IR, and for short circuit R = 0 and hence V =0). But a Zener diode does not obey Ohm's law. Hence even though it's R =0 (it's not really, its an assumption, it's really really small in the reverse breakdown), V need not be zero. Thus there is a 2 V p.d. across the diode and the LED and hence a current will flow through the LED.

[@tnamen1307]

@Khan Academy India - English where is the voltage 3 v if the resistor in series is disconnected from the diode? Zener diode has 2 v. 5 -2 is 3 Vol. Where would this 3 v go???

[@Logadharani]

@@tnamen1307 to the resistor..

[@killiyaswanthkumar9429]

​@@KhanAcademyIndiaEnglish what happens to current in zener diode when we increase the voltage greater than its breakdown voltage in reverse bias

[@prafulkatare1016]

very nice video, please keep on continuing the great work of helping students.

[@tobiefy]

Thank you so much ❤️ finally understood the concept

[@sgtbilko2950]

1st video I've found to properly describe zener diode as a voltage regulator

[@Saryupareen]

Best teacher .......

[@varshaaggarwal9040]

When the input voltage is greater than 2v then the diode acts as a short circuit. Then how can it maintain a 2v constant output? It should be zero.

[@KhanAcademyIndiaEnglish]

That's a pretty good question. Voltage would be zero in a real short circuit provided that it's done by a conductor which obeys ohms law. If R=0 then V=0 (for any value of I). However our Zener diode is a not an Ohmic device. It does not obey Ohm's law. And that's why these things can maintain a non zero voltage across them even if they provide almost zero resistance.

[@tnamen1307]

@@KhanAcademyIndiaEnglish where is the voltage 3 v if the resistor in series is disconnected from the diode? Zener diode has 2 v. 5 -2 is 3 Vol. Where would this 3 v go???

[@malarpandian1187]

@@tnamen1307 it will be dropped at the resistor.

[@sajid279]

In reality yes the led will not glow at a point when v=2 across it but the input voltage change is occuring so quickly that it does not matter or appear two are eyes for such small time gap...

[@chemicallystimulated476]

This is so confusing

[@josephryanperera5620]

when the narrator connected the Zener diode in reverse bias and said TA DAAA! I Felt It Jokes aside this is the so far best video on the internet thank you!

[@shreyakulkarni9240]

OMG I LOVE UR VIDEOS! i always go back with concept clarity and a smile as a bonus :)

[@diya8070]

Really useful Thank u

[@niranjan7457]

Sir at 05:18, you mentioned that only in reverse biased Zener diode, the voltage won't exceed 2 volts. But we can also have it in a forward bias, right? Because even a forward bias has a cut in voltage, at which the voltage doesn't increase much KIndly clarify sir

[@preraj175]

Maybe because the current in forward bias is of the order mA .

[@runzit2007]

Excellent hats off

[@beinghuman1036]

Superb

[@anjalijoshi5901]

Awesome thank you soooooo much 👌👌

[@jagjiwanchimkar8106]

Awesome explaination,thanks for making this video.

[@pratyasa4405]

It is the best video on zener diode.

[@himanshupant3837]

Thanks...much appreciated

[@archanasalunkhe1538]

Best explanation👍👍

[@renukapandit8257]

How does the resistance change as per convinience? Shouldn't the current through the circuit increase to adjust the increase in voltage?

[@KhanAcademyIndiaEnglish]

The Zener diode is a non Ohmic device. This means, unlike conductors, it doesn't have a constant resistance. It's resistance changes with voltage. Below breakdown voltage it's resistance is very high. Above breakdown it's resistance becomes very low

[@renukapandit8257]

@@KhanAcademyIndiaEnglish but sir, I was referring to the resistance connected in series Rs not the resistance of the zener diode 😬

[@KhanAcademyIndiaEnglish]

@@renukapandit8257 Oh, yes, that resistance is definitely fixed. As we increase the input voltage, the voltage across Rs increases (because the voltage across the diode remains fixed at breakdown value). And as you mentioned in your original comment, the current through it does increase according to V = IR. But all that extra current passes through the diode. Hence the current through our LED would still remain fixed :)

[@penumalasunitha14]

@@KhanAcademyIndiaEnglish sir, how you can say that, extra current passes through the zenar diode?.and sir, at breakdown voltage there is high current produces in diode, this current passess back to DC battery and again to all the circuit, my doubt is..if this high current passess through the bulb, won't the bulb damage??

[@priyamehra907]

Best ever explaination

[@tabangatluak8339]

My presentation will be great today because of this video finally understood

[@sandhyaraghavan1028]

Helped me a lot for my boards

[@peeyushgautam77]

Very well explained

[@sanjuktabhowal3624]

very helpful, thank you

[@arshpreetkaur532]

Thankyou 💓😊👍👍✨

[@intibalu805]

Thank you so much Sir ❤️

[@realoneradius3550]

Nice one bro.....simple and plain

[@ashutoshmahapatra537]

The graph done shows I in x axis and V in y axis while it should be opposite, except that its pretty nice video.

[@karthikeyakaza2021]

Sir, isn't there a rule that devices connected in parallel to a voltage source have the same potential difference as the voltage source? By that rule shouldn't the diode and load have the same potential difference as the fluctuating voltage source and be independent of each other's voltages? Is that rule only for Ohmic circuits? If so, why does the rule of increase in current with decrease in resistance in a parallel circuit still apply here?

[@mohamedkalith7607]

Same doubt...did y get the answer?

[@GirijaThangaswamy]

SAME DOUBT. Did you get the answer?

[@padakutamatar7077]

​@@GirijaThangaswamyThe voltage do remains same across zener diodr and led here too. When voltage was less than 2V, the diode acts as a open wire so the entire voltage drop was across led(no parallel arrangemnt) When voltage exceeds 2 volt then the, no mattter what the volt, the zener diode would drop 2v and rest it will allow to pass throughgl. Sinec the led and resistor are in paralled. The voltage across led also be 2v. i dong think i did a nice jpb explaininh this....

[@ranjithkumarr7490]

thank you ji for such a wonderfull explanation

[@akshayarl843]

excellent video

[@nirupamapawar688]

Thank you 😍

[@shaikhsidramahin1492]

Thanks for this 👍🏻

[@ibissaa9695]

You are Electronics god! Hoping you can help resolve my predicament. I have been desperately looking for an answer to WHY the voltage is constant across the diode? I have read and viewed every info possible including going deep into the science of Zener diodes but no one has explained the WHY. One of the reasons mentioned is that the diode regulates its internal resistance to maintain the voltage. How and Why does that occur? Can you please explain?

[@pradipbhandri]

In a zener diode, during breakdown, as current increases, the voltage drop across the diode remains relatively constant. This is due to a combination of factors, including the unique doping profile and design of the diode. Essentially, the diode dynamically adjusts its resistance to counteract changes in current, maintaining a consistent voltage drop. It's like a superhero diode, ensuring stability in the face of fluctuating currents.

[@GirijaThangaswamy]

Thanks!!

[@shaileyshah5132]

Thank you so much

[@Movieverse51]

What if we use pnjunction diode for voltage regulation? It has also breakdown voltage after that it gives zero resistance.

[@arhamkothari2150]

It has a high breakdown voltage. So , for utility purposes, zener diode is used.

[@leandrogarcia6396]

one of the best videos on the goddamn internet :)

[@anandsp1179]

Awesome

[@r.shanmugasundaram7270]

Super sir

[@NOOBGAMER-de3iq]

Best 👍👍👍

[@meerasherin3361]

Can u please again explain what is the purpose of the resistor

[@chappan5615]

The sole purpose of the resistor, in this scenario, is to inhibit the passage of heavy current due to short-circuit which may impair the DC Supply...

[@alphamax157]

but i have a question of the input voltege is less than the breakdown voltage,you said that the diode will behave as an open cirrcuit and the input voltage equals output voltage thats satisfactory but dont you think that the output voltage will still be fluctuating?

[@KhanAcademyIndiaEnglish]

Oh yes, it's not a voltage stabilizer. :). So as the input voltage fluctuates the output voltage will fluctuate as well.

[@alphamax157]

@@KhanAcademyIndiaEnglish but it is used as a voltage regulator. and as i went through ncert the book tries to explain how it can provide constant dc outputs.

[@alphamax157]

@@KhanAcademyIndiaEnglish i have 1 more query, if the applied voltage (which acc. to ncert is the rectified output) first approaches the breakdown voltage and decreases again,will the same voltage(zener voltage) is associated with the diode after the voltage was decreased? Thank YOu for the fast reply.😁

[@swatirani4811]

Ur question is very good

[@swatirani4811]

I too have the same doubt

[@malarpandian1187]

Dear sir is resistance is used for the safety of the voltage supplier.

[@Usuario-ij6oq]

So a regular diode can't be used with the same purpose in other circuit that can face a higher voltage? I think for your explanation in last video that likely it is not possible because of the heat produced in collisions when the voltage breakdown is reached would produce smoke and it would be dangerous, could you confirm it for me?

[@qureius494]

# Sir if i have a voltmeter parallel to the supply and I'm replacing the zener with a switch. So if i get to know from voltmeter that it is exceeding 2V, i can switch on the short circuit. Will it behave the same as with zener

[@KhanAcademyIndiaEnglish]

I really like the way you are thinking. Here is the difference between a switch and a zener diode. When you close the switch, you would create a short circuit of zero resistance (almost). So the voltage across it would also be zero. However when the zener diode acts as short, the voltage across it WON'T BE ZERO. This might seem weird. How can you have negligible resistance with non zero voltage,? This is because zener diode is a non ohmic device. V=IR doesn't work for zener.

[@qureius494]

@@KhanAcademyIndiaEnglish #Thank you Sir /Madam.

[@vivekgupta3692]

@@qureius494 Mahesh Shenoy Sir👍

[@asha8761]

5.38 the diode looks like a dancing doll

[@sachinrath219]

at 2v,the zenor diode breaks off,its still operating at 2v,how its nt getting damaged by infinite flow of current.

[@KhanAcademyIndiaEnglish]

That's the speciality of Zener diode. In reverse breakdown, it can handle large currents without heating up (or getting damaged). Also note, that the current is not infinitely high.

[@Nothing-fp1er]

Sir when the voltage is 2 the diode starts conducting then the voltage across the resistor is?

[@bt-bacheloroftech2678]

Guyss anybody knows which software is this. I am kinda fascinated by this software😅 And ofcourse the teacher too😁

[@thamotharans2106]

Which is effective, is reverse bias zener diode or forward bias junction diode? And which gives more current without any problem?

[@gayatridas7932]

Forward and reverse biased zener diode have different purposes. Forward bias facilitates large amount of current to flow through it only in one direction. So that property is utilised when diodes are being used as full/half wave rectifiers Reverse biaed zener diode is useful for maintaining a constant voltage. In this case we don't want our led bulb to be destroyed by passing more than 2V across it. So here we're looking for something that will limit our voltage and protect the appliance. However , compared to normal reverse biased diodes zener diode is better because -the breakdown voltage for zener diode is lower than the former, so the problem of heating is overcome

[@Leo.Wirabuana]

now I know led have minimum woltage 2 wolt.

[@ankurc]

nice

[@physicsim-possible630]

so if v=vz then the zener diode will be activated but what will be the voltage drop across resistor I m confused even in this it voltage drop should be there since current is flowing through it

[@sakshigupta3067]

I dont know how many people have noticed this..but the signs across the zener diode is wrng!!

[@sachinrath219]

seems the external resistance handles the whole thing and same things are achieved without the zener diode, pl clarify.

[@shipra6812]

Did ya got the answrr?? Im havin the same doh t

[@monalisasahoo171]

Yes I also have the same doubt

[@sachinrath219]

@@monalisasahoo171 the discussion in the video needed more clarity,the external resistance is used only to prevent the zener diode from getting damaged called avalaunch breakdown if connected to higher potential difference(p.d),the p.d across the zener diode remains the same no matter how high is the p.d of the battery,thanks.

[@monalisasahoo171]

@@sachinrath219 okay thank you 🙂

[@alchemist6045]

@@sachinrath219 Isn't the external resistor used to prevent damage to power supply? Zenor diode isn't damaged because of large current.

[@xmenxwk]

I dont get it clearly, why not add the resistor on white wire if we only using it for zener diode? Because if added to orange wire, it will always be dropping voltage.

[@anuragkashyap9888]

Can we use it as a ac voltage regulator?

[@Sushanta-Das]

But when voltage across the bulb

[@aamygee]

If voltage great than 3 will led glow?

[@shashwatpriyadarshy7681]

It will glow with excessive intensity. This is not an efficient way to use a LED as there are chances of blowing it up!

[@askmo99]

I work as a teaching assisstant and make videos online ... Could you tell me the software used for presenting

[@reetichauhan355]

What would happen to zener diode in forward bias???

[@jz7144]

In the forward bias zener diode IV-characteristics resembles that off normal diode but because it wasn't designed to work in forward bias people don't use it there.

[@prav5554]

If zener diode acts as a short circuit, then no current will flow through the loop containing led, then how it remains turn on?? The concept of short circuit is bit confusing here

[@malarpandian1187]

The voltage is constant because the diode and the LED are in parallel connection. Is it right sir.

[@ratikantamahapatra8847]

But LED will not glow after reaching 2V or more!!!!

[@shreejalbhattarai4635]

Why does the led blows up when potential difference hits more than 2 volts?🤔

[@ngkean9743]

so conclude tat the LED wont light up when V bigger then 2V.because it get short circuit

[@harjotsingh20kviews3daysag4]

But why can't we use normal diode

[@jimmycollege3851]

but the led will not light up after adding Rs because it is short circuit

[@kabilanrajagopal5336]

i think u wrongly mentioned + ve and -ve terminal....

[@ligjoe3300]

8:51 , why do you say zener diode is the voltage regulator? when the resistor is actually dropping the voltage.

[@KhanAcademyIndiaEnglish]

It is the Zener diode, that is ensuring a constant voltage come across it right?

[@Nitusingh-tx3fc]

Just a thought Doesn't he sounds like chatur from 3idiots😂

[@paradislander]

this video unfortunately doesn't explain why, when the Zener acts as a "short circuit", why any CURRENT would be left over to power the LED.

[@CSESarathBalaji]

Your voice look like tom holland

[@priyadarshiniab1659]

WHY IS VOLTAGE CONSTANT IN ZENER DIODE?

[@KhanAcademyIndiaEnglish]

This is explained in a little detail in the video of Reverse breakdown voltage. Basically, above the breakdown voltage, there is very little resistance offered for the flow of charges. Thus even if the current changes, the p.d. won't change much.

[@bernarddoherty4014]

WHAT IS A WHOOLT.?

[@santosshresth4419]

why the fk are you pronouncing volts as holts

[@albasit93abl]

ur accent ...😑😑

[@ranjeet5806]

@@bhartiyainfo1723 from where did u studied grammar .... it's more horrible then that "accent" comment.

[@alphamax157]

yeah his accent is obviously better than yours.😑

[@bhartiyainfo1723]

So don't see khan academy videos on KZbin