Solved Problems on the Zener Diode

[@ALLABOUTELECTRONICS]

The timestamps for the different examples solved in the video: 1:15 Example 1 5:55 Example 2 9:55 Example 3 14:33 Example 4

[@sandeepmukhrjee2476]

Sir, I have doubt in this example 3, Can you please explain me. As vin is increasing from 20-30 volts Can you tell what is the value of load current and zener current when Vin=25 volts?

[@ALLABOUTELECTRONICS]

@@sandeepmukhrjee2476 If Vin is 25V fixed voltage, then Is = 19.2 mA. Zener Knee Current is 0.5 mA. Therefore, maximum load current is 19.2 mA - 0.5 mA = 18.6 mA.

[@sandeepmukhrjee2476]

@@ALLABOUTELECTRONICS No no sir...you got me wrong, I am not changing any statement of the question. I am saying, as it is mentioned that Vin is increasing from 20 to 30 volts. So, when Vin=20 volts then, then Iz = 0.5 and IL = 13.7 When Vin=30 then Iz= 10.5 and IL= 13.7 And when Vin=25 then Iz= 5.5 and IL= 13.7 Does this mean IL is fixed ? Is my above analysis is correct?

[@abhishekbhandari4359]

@@ALLABOUTELECTRONICS sir, at 13:50 you said If we choose 23.7mA as the maximum current then the circuit will not work because at Vin=20, the input current is 14.2mA which is less. Sir my question is, the input current is less then what is the problem? It can be possible that at Vin=20 volts. Iz=0.5mA and IL = 13.7mA Although it is less than the maximum value but it can flow through load. Right?

[@Palkhushaboo]

@@ALLABOUTELECTRONICS 14:00 , sir when u calculate soure current ,the units are not same i.e. numerator is in volt & denominator is in kilo ohm . How it can be done?????as

[@frankreiserm.s.8039]

I am a 51 year old person (I have a lot of life experience) and I have many degrees. So, I have authority to say this: You are very smart and very intelligent. I own my own electronics repair shop, and I build electronics. I greatly appreciate your videos. Frank Frank Reiser Video/Audio Service

[@jitheshdsouza98]

dont care cope

[@ajinkyadhekne]

This is one of my favorite KZbin channel for electronics.. You have explained very difficult concepts in simple and concise manner with simple explanations and beautiful examples and derivations.. Also you have made very good use of the animations which makes understand things very easily.. Keep making videos.. Thank you and all the best..! :-)

[@Metadel-c2c]

within a short time you successfully provide a plenty of knowledge.thank you so much.

[@srisaisubramanyamdavanam9912]

Sir ur really a thop My teachers didn't explained me like this

[@vishvakapadiya3051]

@ 14:13 always had doubt that why 13.7 and not 23.7 but you explained it so simply. Thank you ❤️

[@sandeepmukhrjee2476]

I have doubt in this example, Can you please explain me. As vin is increasing from 20-30 volts Can you tell what is the value of load current and zener current when Vin=25 volts?

[@vishvakapadiya3051]

@@sandeepmukhrjee2476 when Vi = 25V, Is = 19.2mA and Iknee(zener) = 0.5mA, which makes Iload = (Is - Iknee) = 18.7mA. Hope it helps!

[@sandeepmukhrjee2476]

@@vishvakapadiya3051 according to you, for Vin=25, IL is 18.7 then how IL maximum is 13.7mA? In the question it is mentioned that, for Vin=20-30volts find the IL maximum.

[@vishvakapadiya3051]

@@sandeepmukhrjee2476 the reason is, if we use any value beyond 13.7, like 23.7. Then, at 20V Vin, zener diode could not work as it can not even have knee current (as Iload itself takes large value). Thus, circuit is off. And in question maximum current required so circuit can function properly. Thus, ILoad maximum is 13.7

[@abhishekbhandari4359]

@@vishvakapadiya3051 If we choose 23.7mA as the maximum current then It can be possible that at Vin=20 volts. Iz=0.5mA and IL = 13.7mA Although it is less than the maximum value but it can flow through load. Right?

[@parashardeb9716]

I really didnt understand 5:40 like why is the worst case where load resistance is infinite doesnt that mean all the current will pass through the diode and hence more power generated as power is directly proportional to current flowing through it

[@sreejachakrabarti337]

Thank u so much sir. U explained so nicely.. I had great problem with these diodes .. this was very very helpful. Great teaching. Please upload more videos on solving physics questions (modern physics ). Btw am an neet aspirant.

[@malingatembo8850]

You deserve a Nobel

[@ernestgyamerah3261]

Why is the power rating not properly called maximum power rating since you used the maximum current the zener diode can take?

[@swedensy]

You are doing it over cemplicated.

[@yoursufferer8794]

Great video Sir! You deserve a lot more subs!!

[@arpitamunsi1332]

@ 5:30 why the maximum ('worst possible case') zener current has been considered for calculating minimum power rating of the zener diode?

[@ALLABOUTELECTRONICS]

The minimum power rating is the minimum required power rating of the Zener diode with which it will work with the given load and voltages. That means whatever Zener Diode we select, it should be able to withstand the worst possible case current. If its power rating is more than that, then definitely it will work in the given circuit. I hope, it will clear your doubt.

[@indeedhid380]

Previous video, RLmin = (Rs*Vz)/(Vs-Vz) = 100 Ohm .. What happened? Both seem logical to me hence the confusion.

[@ALLABOUTELECTRONICS]

In the previous video, during all the examples it was assumed that the Zener Knee Current is Zero. (Izk = 0). But here it is non-zero. In this example, if you consider Izk = 0, then you will get 100 Ohm. I hope it will clear your doubt.

[@indeedhid380]

@@ALLABOUTELECTRONICS Thank you!

[@indeedhid380]

@@ALLABOUTELECTRONICS So if I had a non negligible resistance (i.e not this video), it'd become correct just by using Vz+Rz*Izk instead of Vz. Else if the resistance is negligible but we have a knee current, I should analyse the circuit for the minimum values using currents because elsewise I'd loose the Izk since Rz is null right? Please correct me if I am wrong.

[@vishalk8008]

in example 3 why didnt u take the maximum value of load current as 23.7A? i didn't understand that part if we take 23.7 as maximum anything below that current can also exist as make the zener to function properly right

[@ALLABOUTELECTRONICS]

As, I mentioned at 13:50, if we select 23.7 mA as the maximum load current then the circuit won't work when the input voltage is 20V. Because at that time, the supply current Is is 14.2 mA (which is less than 23.7 mA). During the design, the max. allowable current should be such that the circuit should work properly for the entire input range. For example, if we connect the load according to 23.7 mA ( 5.8V/ 23.7 mA), then the circuit will work at 30V, but it won't work at 20V. Because the supply itself is less than 23.7 mA. So, with that design, if we select the min value of the load or max. allowable current (for regulated output voltage), then the circuit won't work at 20V. I hope it will clear your doubts.

[@vishalk8008]

@@ALLABOUTELECTRONICS does it mean that the current through zener must be equal to or greater than max current? If this is so then y is it called max current?

[@ALLABOUTELECTRONICS]

See, when we say max.current, it's the max. current which is allowed through he zener diode to work it properly as zener regulator. Similarly when we say, max. Load current, it's the max.allowable current through the load which will ensure that the zener diode operates as a voltage regulator. The current through either zener diode or the load should be less than the max. limit.

[@randomstuff9960]

Really helpful.... must appreciate

[@anjanadhar02]

Nice video sir But I had a question Suppose we are asked what is the output voltage...does that have a specific formula or it's like zener voltage is equal to output voltage?

[@ALLABOUTELECTRONICS]

If the series resistance of the Zener diode is assumed to be zero , then yes output voltage is equal to Zener voltage. Unless the series resistance is specified, Vout = Vz when Zener diode is operating in the breakdown region.

[@susantabhattacharya6323]

Please make a video on ISRO preparation to achieve a high score in written exam. It will be very beneficial.

[@neerajgodara479]

A zener diode has a resistance of 5ohm .if the current through the zener diode changes from 10mA to 20mA, then change of voltage across the zener diode will be (1) 0.05v (2) 0.1v which is correct explain in detail Thanks Sir

[@activebrains9205]

Superb explaination🔥❤️❤️

[@SantoshYadav-bx2yk]

Bgvan aapko khus rkhe great work

[@googlearthtest12]

What would happen (w.r.t Example 1) if we select RL less than its minimum value (125 ohm). Let's say we connect RL with value of 90 ohm, what would happen to Vz? Will it remain 5V or drop? 2. What would happen (w.r.t Example 1) if we put 3v LED as RL in the circuit?? What would now be the voltage across zener diode (Vz) ?

[@acousticankit4408]

In example 1 ..why we are considering only one resistance while calculating total current we should also take load resistance ..plz clear my doubt..

[@ALLABOUTELECTRONICS]

I think you are talking about the current Is right ?? It has been found using the nodal analysis method. The voltage at the twp node is known. (Vs and Vz). The current which is flowing through the resistor is equal to (Vs - Vz) / R. I hope it will clear your doubt.

[@jasminebano8051]

Awesome explanation sir ,,, thanks a lot!

[@anishamajumder1940]

in last ques why are we taking r

[@gopalk371]

One question , in the first example how to find the RL max ?

[@ALLABOUTELECTRONICS]

To find the RL (max), first Iz (max) should be known. That is the maximum Zener current which Zener Diode can withstand. In this case, it is not given. But if it is given then considering that value of Iz, you can find the maximum value. I think I have already covered one such example. Please check the diode and diode application playlist. You will find it there. In case, if it is not covered then let me know. I will surely cover it on the second channel.

[@shahalamshahin8443]

In the case of maximum power rating we use maximum current ( see electronic devices and circuit theory by boylestad 10th edition example 2.27 (b) ). But for minimum power rating you have used maximum current. Is it right???

[@ALLABOUTELECTRONICS]

Would you please mention the timestamp where you are referring to ? It will become easy for me to answer your question.

[@shahalamshahin8443]

Please see example no 2.27 of electronic devices and circuit theory by robert boylestad 10th edition.

[@tushartomar8664]

yes, i think u are right as he used maximum current instead of using min. current passing through diode to find out min. power rating

[@zehrazahoor7855]

Why didn't we consider the resistance of diode in example 3?

[@ayiedaus8841]

how if the value of Rs and R load are not given?? how to find Rs and RL??

[@kumarbheesham5572]

Sir how to solve the given below problem Consider a peak rectifier fed by a 60Hz sinusoid having a peak value Vp=100V. Let the load resistance R=10kohm. Calculate the fraction of the cycle during which the diode is conducting.

[@me28naveenkumaryadav31]

A lot of thanks sir Very nice classes

[@bwireeddy3474]

but sir i thought to get the minimum zener power rating, the resistor should be selected such that its reduced

[@bhartibhatia2232]

17:04 i didn't understand that why we chose R for Vin = 30V, why didn't we find R when Vin=50 v?

[@ALLABOUTELECTRONICS]

Our aim is, the value of R should be such that, the circuit should work properly as a Zener Regulator. Here, IL is fixed and Izk is fixed. So, we know the minimum required current Is (Is min). With our selected value of R, if we are able to get Is (min), then the circuit will work properly for higher supply currents. At that time, the current through the Zener diode will be Is - IL. So, here for the given value of R, the minimum value of Is will occur when Vin is minimum. That is 30V. And that's why, the value of R is found when Vin = 30V. If the circuit works properly when Vin = 30V, it will also work when Vin = 50V. I hope, it will clear your doubt.

[@namithak3128]

sir, how did u calculate v0 value in example-2 replyy plzz.....

[@rahulmagotra4098]

Sir i didn't get how u select 13.7 mA as max current plzz explain

[@lokeshthakur3076]

@@ALLABOUTELECTRONICS no sir using v=30, the current through the battery is 24.2m plzz check the equation again

[@ALLABOUTELECTRONICS]

if we select 23.7 mA as the maximum load current then the circuit won't work when the input voltage is 20V. Because at that time, the supply current Is is 14.2 mA (which is less than 23.7 mA). During the design, the max. allowable current should be such that the circuit should work properly for the entire input range. For example, if we connect the load according to 23.7 mA ( 5.8V/ 23.7 mA), then the circuit will work at 30V, but it won't work at 20V. Because the supply itself is less than 23.7 mA. So, with that design, if we select the min value of the load or max. allowable current (for regulated output voltage), then the circuit won't work at 20V. That's why 13.7 mA is selected as max current. I hope it will clear your doubts.

[@tula__]

Thanks. Subbed!

[@yoursufferer8794]

7:30 How V(output)=7V + 10ohm*Is ??

[@travellerhasib5522]

It's 7v+V10 And V10= 10ohm*Is

[@def1NY]

@@travellerhasib5522 Hey Traveller... your explanation it's 7V + V10 and... V10 = 10ohms*Is confused me... to what does V10 refer? is that Ten Volts?? Is that V with number 10?? What is that?

[@pasindumalshan3344]

In zener voltage zener diod can transfer the current (in VI characteristics) so why the current pass through the resistor what's the process of that. please help me

[@Tyagi_anant99]

At 5:51 if we are calculating power minimum then shouldn't we multiply knee current to zener voltage which will be equal to 5*10 = 50 watts 😮‍💨

[@sandeep_nit_j]

i too thought the same

[@josedominguez2021]

Fantastic!!! 1K likes!!!

[@sounerds1211]

Then how are we going to get the RL(min) and IL(min)?

[@ayasatja9713]

If we put R load on example 2,will it be different?

[@mayurshah9131]

Excellent

[@prakashchandradalai3512]

Example 1 minimum resistance is 100ohm if we apply direct formula and u got 125 ohm .then which one is correct.please reply bcz lots of confusion arises

[@ALLABOUTELECTRONICS]

The direct forumla is applicable when it is assumed that Izk is negligible. Here, the value of Izk is given. So, if you consider the Izk then you will get 125 ohm. In the question if Izk is not given then you can assume it zero. And you can apply the direct formula. If it is given, then you can solve as shown in the first example. I hope it will clear your doubt. If you still have any doubt then do let me know here.

[@prakashchandradalai3512]

@@ALLABOUTELECTRONICS thanks

[@abhilashvadali457]

@@ALLABOUTELECTRONICS sir is there any reason why we should consider like that way?

[@sheetalmadi336]

@@ALLABOUTELECTRONICS but why is it so sir? Is this because,the consideration of Izk will always give thevenin voltage greater than Vz?

[@ashutoshdwivedi5148]

Thankyou sir🙏❤️

[@sandip_kanzariya8476]

Nice 👍 ....

[@sagar8234]

What about the maximum power rating in first example ?? Help anyone

[@ALLABOUTELECTRONICS]

Here the minimum power rating refers to the minimum power rating required of the Zener Diode such that, it can operate with the given configuration of the supply voltage and the resistors. That means the selected Zener diode should have the max. power rating of at least Pz min (which is found in the example). I hope it will clear your doubt.

[@becausehelivees4672]

how about a positive minimum current then a negative maximum current.

[@krishkrishna4810]

Hi sir,75-0-75 volt 10amp, how to drop voltege 50-0-50,using zener diode.

[@rupamghosh2020]

Sir can you pls suggest a best book to read the zener diode ?

[@ALLABOUTELECTRONICS]

1. Electronic Devices And Circuits Theory 10th Edition (English, Paperback, Robert L. Boylestad, Louis Nashelsky) 2. Electronic Principles (SIE) Paperback - 1 Jul 2017 by Albert Malvino (Author), David Bates (Author)

[@rupamghosh2020]

Thank you very much sir.

[@gavinreynolds-jones9212]

At 2:48 what is IZK?

[@gavinreynolds-jones9212]

NVM Zener knee current!

[@ALLABOUTELECTRONICS]

It is the minimum required current through the Zener Diode, to use it as a voltage regulator. If the current through the Zener diode is less than that then it won't provide constant voltage.

[@bhagyashrinalawade6923]

Please clear my doubt at 14:16 how to choose answer

[@ALLABOUTELECTRONICS]

First we have calculated the minimum value of the series current which is supplied by the source. Even at the minimum current, the circuit should work. From that, the zener knee current was subtracted, because that much current is required to operate the zener diode. And the remaining current is available for the load. So, the remaining current ( Is - Izk) is the maximum current which can flow through the load. Or in other words, while selecting the load resistance, its value should be such that, the current through the load is not more than 13.7 mA. If it is more than that then circuit will not be able to supply that much current. ( When it is operating at 20 V). Of course it can supply that current at 30 V, but during the design we should always consider the worst case scenario. I hope, it will clear your doubt. If you still have any doubt then let me know here.

[@swapnilkale394]

RL min value is incorrect in example 1. It must be 100 ohm

[@gluttony4778]

consider knee current

[@mohammadnuman260]

Nice work.....!

[@KRISHNAVERMA-kv07]

why current is added with voltage to get output voltage 8:35

[@ALLABOUTELECTRONICS]

Using ohm's law, the voltage drop across 10 ohm is calculated ( 10 x 3/ 210). And the overall output voltage is 7V + voltage drop across 10 ohm resistor. I hope, it will clear your doubt.

[@NiteshKumar-qd9zu]

Very good And thanks...

[@prithvirajsingh9987]

Thank you sir

[@sourabhkrishnataw1013]

minimum power rating, Pz=Vz*Iz when Iz=Is , how power is minimum? it should be maximum!!

[@ALLABOUTELECTRONICS]

Here, the minimum refers to the least power rating requirement of the Zener diode. That means if you are going to use some Zener diode for this circuit then its power rating should be more than that. I hope it will clear your doubt.

[@imabhishek028]

thank you :)

[@unique_Nature_Source]

jener me maximum Power negative ho sakta hai

[@AshishKumar-hb3uj]

Similar ques asked in jee mains 10jan shift-2

[@shumetshegaw9019]

Hy,sis you seem sweet .isn't it ?

[@ihaveagoal4665]

@@shumetshegaw9019 lol simp

[@163praveenashridharshini9]

Ossssssm video sir

[@amoghsv557]

Thank you so much

[@technology8436]

Wow

[@md.isharulhaquenuhas4508]

thank u

[@hichambenbrika4211]

at which level they study this type of problems in india ?

[@parminagaba7699]

Best

[@wolfgangboettcher3126]

Doppelt hält besser

[@sayalijamadar2769]

@ 4:06 doubt hai

[@ALLABOUTELECTRONICS]

If the value of load resistor is less than 125 ohm then the current through the diode will exceed its maximum current rating. And that can damage the Zener diode. I hope, it will clear your doubt.

[@sayalijamadar2769]

@@ALLABOUTELECTRONICS thanks 👍

[@felipevenegas6061]

I love you

[@tanberhasanshemanto2179]

999

[@albertmaimom9867]

Sorry but your teaching is a bit tough