How to identify the Saturation in BJT? What is Hard Saturation? Transistor as a Switch Explained

[@ALLABOUTELECTRONICS]

The timestamps for the different topics covered in the video: 1:03 BJT in the Cut-off Region 2:21 How to identify the Saturation in BJT 4:31 Solved Example ( Identify the Region of Operation of Transistor ) 7:10 What is Hard Saturation in BJT 8:07 Solved Example on Hard Saturation 9:40 Transistor (BJT) as a Switch For more Solved Examples on the BJT, check out this playlist: kzbin.info/www/bejne/mKqzc42jeMummJo

[@thelegendarychicken8831]

I have gone through so many stack exchange posts, videos, and readings to find the information that your video gave and clear up t he misunderstanding that I had. Thank you so much for this video!

[@alpali2330]

Thank you, very thorough. :) I had to do some uni assignments after missing a couple of lectures, haha. I'd just add, that if the Vcesat is given, Icsat = (Vcc-Vcesat)/Rc.

[@x3mfck]

Thank You ... I did have to slow down the video to verify the math and grasp the concepts , but over all the lecture was well explained ..once again Thank you.

[@don5nake]

Excellent video, very well explained - thank you!

[@kadirtetik805]

Thank you so much sir. Very clear description finally I understood it :)

[@michaelcostello6991]

Wonderful practical educational video. Thank you.

[@martinchan5013]

Thanks for the crystal clear explanation.

[@benrich6376]

This video was excellent. Thank you.

[@RexxSchneider]

Well done. You covered all of the practical cases that would be encountered in real applications of a switching transistor. However, for students, you are much better off teaching them to identify saturation by comparing the ratio of the saturation collector to the real base current with the transistor β, as you did at 6:20 and showing that when the transistor is in saturation, its current gain is significantly less than its current gain (β) in the active region. If you stick to this method, nobody gets confused by imaginary collector currents such as the Ic=4.65mA that you calculated at 5:33 or the Ic=9.3mA that you calculated at 12:00 (using the test of whether the actual current gain is significantly less than β only deals with real currents, so less confusion). One other small point: your calculation of the transistor's output impedance in hard saturation is naïve. In reality, the change in Vce(sat) with current is very small, typically around 200mV for a change in collector current of around 100mA (viz. BC547 datasheet), thus giving a dynamic resistance of around 2 ohms, and of course, it's the dynamic resistance that's important in real applications.

[@alejandroperez5368]

Germans love to complicate things always, don't you guys?

[@sanghapriyochoudhury8859]

Tnx.. cleared my confusion

[@sjlee6913]

Very good lecture about bjt as a switch!! Thank you!!

[@chathurikadilhani1951]

Very clear explanation ❤️🙏thnk u

[@Rajesh-cf8zx]

Very very concept clearing video

[@praveenbijaraniya3106]

Bravo....cleared every doubt.... marvellous...

[@vincenth1871]

阿三这口音我真是服了

[@rf-sn7dx]

哈哈哈哈

[@mehmetsahin8261]

Adamın dibisin sen. You are realy great man bro

[@hemanthsaiborra106]

Excellent explanation even better than lecturers

[@ratnakumarikillada2250]

Excellent explantion, it is very usefull

[@susantamondal3035]

Great explanation

[@Yusuf-dx4hw]

Thank you so much for your labor.It came to me complicated at the beginnig but after your examples i got it very clear.Greetings from Turkey

[@anwaydas1220]

greetings to turkey from india

[@priyajitmondal6661]

Thank you so much sir ❤️🥺🙏👍

[@abhinavsoni1805]

Very nice explanation.....

[@megharaj5384]

very helpful👍

[@jitanshushaw359]

Sir please please add a video about frequency response systems.Thank You.

[@joshithmurthy6209]

Thanks bhaiya

[@pbeee2417]

Thank you sir

[@Fifty60]

Very nice!!

[@Recapsins99]

Thankyou ❤️

[@mayurshah9131]

Very good 👍👌

[@VersatileAnthem]

the way you explain in your videos concepts become crystal clear.love from Bangladesh..

[@prashantsoni0803]

For npn transistor, practically Vcb >(-0.4) for active region. Please explain why the characteristics shift backward beyond origin.

[@RexxSchneider]

Assuming a silicon npn transistor: in saturation, the base-emitter junction is forward biased, so must retain a voltage drop of around 700mV. So Vbe ≈ 700mV. However, the collector will still attract charge carriers from the emitter with as little as 100mV between collector and emitter, so Vce(sat) could be as low as 100mV or so. The collector doesn't have to draw any current from the base, so the voltage at the base relative to the collector is immaterial, and the collector will still drive current through the emitter even when it is has less voltage that that at the base.

[@prashantsoni0803]

Which is the best biasing to be used to make the BJT in hard saturation for the same values of Rb ? For eg, we studied various biasing fir the best amplifier so that Q point will be in active region ,which is best biasing for BJT to be used as switch. Please explain .

[@RexxSchneider]

That was explained in the video. To ensure saturation for any small signal transistor set the base current to be 1/10 of the maximum collector current for the circuit you are building. You only need Ohms law to calculate the collector resistor when you know the supply voltage and the required current, and Ohms law again will then give you the base resistor when you know the driving voltage.

[@ajay-dp2si]

Ye btayiye ke jab power electronics me bjt as switch use krte hai to base current ko consider kyu nhi krte

[@anmolpardeshi3138]

What is the difference between (in terms of what is the type of output (voltage or current) and where that output is taken) circuits for BJT as a switch and BJT as an inverter.

[@ALLABOUTELECTRONICS]

Well, when it is used as switch then load is connected at the place of collector resistor (mostly).

[@umeshgowda4704]

Which software use to create this vedieo

[@ismail.eee18bsmrstu]

11:17 , Why we have assumed the Reverse Saturation Current (Ico) is equal to 5uA . ???

[@valee_mayzar]

Hi if you are not given the Vce(sat) do you assume that Vce(sat) =0V in the calculations to determine whether the transistor is saturated or not?

[@ALLABOUTELECTRONICS]

Yes. Typically Vce (sat) is 0.2V. But if it is not given, then it can be assumed as 0V to determine the operation of the transistor in the particular region.

[@periohome7760]

great vid. at 9:03 in the video where/how did you get Vbe as 0.7v?

[@ALLABOUTELECTRONICS]

It is the typical voltage between the base-emitter junction. Much like a forward voltage drop across the silicon diode. If the value of Vbe is not given then it can be assumed as 0.7V. Actually, for transistor to transistor, it may change with the operating point. (Not by much though). But for estimation, it can be assumed as 0.7V for the calculation.

[@sagar-oi3kv]

Try to write down the region when you take the equations

[@danielagutierrez9985]

The emisor is connected to ground?

[@black-sci]

In cutt off why Vbb=0 it can be negative and Why Vce=0 for saturation region. Also in input characteristics and output characteristics we only discuss zero or fairly low negative voltage for REVERSE BIAS.

[@RexxSchneider]

Until the Vebo (maximum reverse voltage for b-e junction) is reached, a transistor with a negative Vbe will pass the same current as when Vbe = 0, so you don't need to worry about a separate case. Vce is not actually 0V in saturation, but it is only a few hundred millivolts at most. Compared to the supply voltage, that will generally be negligible, so using Vce = 0 is normally an acceptable approximation.

[@ayushdewangan3792]

Make videos on overdrive factor and Beta forced

[@farhanupaul]

How are we controlling the Vce to keep it near zero for cutoff? Is it by having IcRc=Vcc?

[@ALLABOUTELECTRONICS]

Larger collector current Ic means, large voltage drop across Rc. ( IC*Rc). And hence VCE will reduce and will operate the BJT in saturation. In cut-off, Ic is almost zero, so VCE is approximately equal to Vcc.

[@farhanupaul]

@@ALLABOUTELECTRONICS Thank you sir

[@AnoNymous-po5sx]

Sir, I have a doubt. It is said that in saturation region, both the diodes will be forward biased. But clearly in the saturation mode, Vc is taken positive when compared to Vb(20V and 10v respectively). Since collector is n type, shouldn't it be more negative? This question is bugging me a lot. Please help.

[@ALLABOUTELECTRONICS]

In the saturation, if you are aware, the Vce (sat) is around 0.2V. If emitter is connected to the ground terminal, then Vc will be 0.2V right !! Vb is at around 0.7V, Since Vbe = 0.7V. So, Vb> Ve and Vb > Vc. So, both junctions are forward biased. I think what you are talking is the supply voltage at the base and collector (Vcc and Vbb). But there will be a voltage drop across base resistor Rb and Rc. So, voltage at the base and the collector will be different than Vbb and Vcc. I hope it will clear your doubt. If you still have any doubt, let me know here.

[@AnoNymous-po5sx]

@@ALLABOUTELECTRONICS Yes. Sorry that I completely ignored the Rb and Rc voltage drops. 😂 Thanks for clarifying. A big thumbs up!👍

[@RexxSchneider]

@@ALLABOUTELECTRONICS Actually, in saturation, the base-collector P-N junction is only forward biased by at most around 500mV. That is insufficient for any appreciable current to flow (a few nanoamps for most silicon junctions), so that becomes completely negligible compared to the milliamp-level currents flowing from base to emitter and from collector to emitter.

[@rajendranluxmikanth6106]

If Ic < Ic(sat) what will happen?I mean the what is the mode of the transistor in that condition???

[@ALLABOUTELECTRONICS]

It will be in active region.

[@rajendranluxmikanth6106]

@@ALLABOUTELECTRONICS okok.Thank u

[@ismail.eee18bsmrstu]

08:41 , For Hard Saturatin, We used here Beta as 10. Why did we not use Beta as 50 which was given in the circuit here.?? Nor in The ckt there will be mentioned any value of beta, but we have to use for Hard satuaton by understanding.?

[@ALLABOUTELECTRONICS]

It is the typical value. The beta value given in the circuit is for active region. For, saturation region, according to the base current (how fat the transistor is in the saturation region), the beta value will change.

[@eunicedeepthivanka8958]

Sir,why is transistor considered to be in saturation when Ic is greater than Ic (sat)

[@ALLABOUTELECTRONICS]

Ic (sat) is the maximum current transistor can supply with the given value of Rc and Vcc. It's like when you connect a resistor Rc to supply voltage Vcc, then current which can flow through it is Vcc/ Rc. So, considering Vce zero for a moment, it is the maximum current which can flow through the collector. (it is defiend as Ic (sat)). When the calculated collector current Ic is more than Ic (sat), then the transistor can not supply more than Ic (sat). Or in other words, it can be said that the transistor is operating in the saturation. I hope it will clear your doubt.

[@eunicedeepthivanka8958]

ALL ABOUT ELECTRONICS understood,thank you for making a video on this topic,is there any possibility to understand this concept from output characteristics of CE configuration

[@chanakyasinha8046]

@@eunicedeepthivanka8958 its shot circuit

[@ghanshyam3177]

Sir when there is a resistor Re in common emitter then how we find

[@ALLABOUTELECTRONICS]

Find the voltage VCE as if the BJT is operating in the active region. If it is in the saturation region then you will get negative VCE. or second way, both base-emitter, and collector-base junctions are forward biased in saturation. So, that's the other way you can find the region of operation of BJT.

[@mofajjelfakir70]

Make a video on physics of semiconductor devices

[@ALLABOUTELECTRONICS]

Some videos on MOSFET and JFET have been already made. Please check the playlist.

[@bishalmondal5543]

datasheet provides a range of beta values. How do we decide which beta to select?

[@ALLABOUTELECTRONICS]

In the datasheet, the different values are given for the different operating currents and voltages (Ic and Vce). Based on your required operating condition, you should choose the nearest value of beta for calculations and design.

[@kanchanarora5410]

👍👍👍

[@hamzasaim5912]

Ic(sat) is the maximum current.. Then how is it possible that Ic>Ic(sat) ❓❓

[@ALLABOUTELECTRONICS]

It can't be greater than that. In fact, during the calculation, if calculated Ic is greater than Ic(sat) it means that the transistor in saturation. The thing is, during the finding whether the transistor is operating in active or saturation, the value of beta which is used for the calculation is for active region. In saturation, the beta reduces. I hope it will clear your doubt. For more, info you can go through the examples on BJT on the second channel. Many similar examples are covered there.

[@niharikagoulikar2921]

@@ALLABOUTELECTRONICS IcIsat then it operates in breakdown region and transistor eventually gets destroyed..🤔😑

[@RexxSchneider]

@@ALLABOUTELECTRONICS This is why it's better to compare actual current gain with β, and then you know that the transistor is in saturation when the current gain is significantly less than β. Avoid the confusion caused by calculating impossible currents.

[@radioactive0761]

This is confusing because my prof told us that if Vbb is smaller than Vcc it will automaticaly be in active region and if Vbb is bigger than Vcc it will be in saturation region. Please explain to me because your Vbb is 10V and Vcc is 20V therefore it will not be in saturation. 😣😣

[@ALLABOUTELECTRONICS]

It’s not always necessary. You also need to consider the base resistor. With large value of Vbb, if you also use large value of Rb, then it’s quite possible that the BJT is still in active region. Rather just looking at the voltage levels of supply, you should check the condition which I have mentioned in the video.

[@ankurkar7985]

what happen if Ic=Ic(sat)?..........saturation region or active region???!!!

[@ALLABOUTELECTRONICS]

BJT will operate in the saturation.

[@rajbalachandran9465]

1000 likes 💖

[@justchill4873]

Sir transistor as an amplifier??

[@ALLABOUTELECTRONICS]

Please go through the BJT playlist on the channel. You will get the videos. Go through the videos on small signal analysis. All configurations (CE,CC,CB) have already been covered.

[@nayanakv2382]

Sir why we assume Vce = 0 when it is in saturation region?

[@ALLABOUTELECTRONICS]

In saturation region of operation, typically Vce is around 0.2 to 0.3 V. And when BJT is used as a switch then it is used in the saturation and cutoff region, where it acts as on or off. In saturation, since Vce is very low, for digital circuits it can be assumed as zero. ( very low voltage drop). I hope it will clear your doubt.

[@nayanakv2382]

@@ALLABOUTELECTRONICS sir, Is it because in saturation region of operation since both junctions are forward biased the electron flow from emitter to collector is very small? So that Vce is small?

[@ALLABOUTELECTRONICS]

@@nayanakv2382 If you see the collector and emitter current, then they are comparable. But since base-emitter and base-collector junctions are now forward biased, the difference between emitter to collector voltage Vce is very small. For the NPN transistor, If the emitter is at ground potenital, then the base is somewhere around 0.6 to 0.7V. In saturation, since the base-collector junction is also forward biased, the collector is also less than the base voltage. (Typically 0.4 to 0.5V less than base voltage). Hence, Vce is around 0.1 to 0.2V in saturation. I hope it will clear your doubt.

[@nayanakv2382]

@@ALLABOUTELECTRONICS yes sir clear 👍🏻

[@ajay-dp2si]

Why base terminal is not shown in bjt as switch while without given base current bjt never be on

[@ALLABOUTELECTRONICS]

It’s just analogy. In typical switch symbol, we do not have third controlling terminal. Switch is either ON or OFF.

[@ajay-dp2si]

@@ALLABOUTELECTRONICS sir semi conductor me Atom ko sphere se Show kyu karte hai

[@ajay-dp2si]

@@ALLABOUTELECTRONICS aur jab doping karte hai to dopant ko centre me kyu Show karte hai

[@goranvuletic8873]

Good that you added subtitles, beacuse the accent is unbearable, I can't understand 30% of what you pronounce.

[@anshadedavana]

The tutorials are mostly aimed towards Indian engineering students. Naturally, Indian English is used and those who are from outside will have a hard time understanding it. But there are a lot of videos that are already available about electronic engineering in US and UK English , hence there is really no need to follow this videos anyway.

[@otenyop]

@@anshadedavana l agrre with you absolutely. The target audience is different. MIT and Cambridge Universities have the same content online...

[@mumin832]

I don't know why every video I search there is always Indian, u messed everything Indian people. 😒😒

[@manivannanselvam3525]

😂🤓we are trained hardly in that way...