Thanks bro. I wish you taught my analog electronics class. My professor is known as Prof. Power Point.

Outstanding teaching; clear, concise and neat. The best explanation on KZfaq.

Best video on Small signal as far as i have seen. Wish I had this while i had the course.

Finally I really get it, thank you. We put together a circuit like this in class yesterday and we really didn't quite understand what we were doing, despite many weeks of prestudies. So many teachers are just all over the place and wants to teach everything at once, making it incomprehensable.

This has to be the best video on the topic in all of KZfaq. Thank you for making this!

I usually don't leave comments on KZfaq videos but this video really helped me. Thank You!

This is amazing!! I had been looking for so many videos, but this is the actual video that I could understand !! Very detailed explanation, love it. Hope you could keep making video with such good content and excellent presentation.

I'm studying these topics for the doctoral program interview. I studied from the book during my undergraduate education. Your expression is very nice and fluent. Thank you from Turkey :)

Best lecture ever ! Thank u

I'm so glad I've found this video, you don't know how this helped me. Not only I learnt how to re-draw the circuit into equivalent one, but I also revised the circuit solving. Thank you.

I wish I could give more than 1 like. Thank you for the effort that you've put in to explain clearly.

Very clear, concise, and easily applicable to other amplifier circuits....much easier to understand and apply than the electrical circuits courses I took in school....

Thank you very much sir for your generosity in sharing this very needed knowledge and delivering it in the most effective way. From now on wards I'm a subscriber. Thank you again. God bless you sir.

Amazing explanation. Thank you

This is by far the best video I've watched on youtube about any topic on EEE. So so good and nicely explained.

Immensely valuable video ! A video to be seen many times and studied thoroughly ! Enormously helpful !!!

This video has helped me a lot. You are a great teacher. Keep up!

This was so well done! Other videos do not cover concepts that are essential for a clear understanding. Your teaching is truly unique and does not even allow for confusion to arise. I would suggest a next video for an emitter follower however with watching this video I can figure it out on my own.

Thank you to make me understand in a half-hour while uni. prof couldn't in weeks.

Very elegant explanation. Great video.

Test tomorrow. Great refresher! Very clear and concise.

It was a very clear and nice explanation. I have seen a lot of videos but it was really good considering you have showed the logic behind the analysis instead of random formulas. Thank you so much, sir.

Fantastic job! Well thought out examples. I really appreciate the thoroughness put into this video.

I learned and understood more from this than I ever did in my electronic devices class. It's too bad that many people assume this is the level of instruction they will receive when attending a university - if this level of clarity and explanation was the standard, tuition prices may be a little more justified.

Fantastic explanation!

Really good and understandable presentation of the subject and the mathematical background. There is a lot of substitutions work to do. But anyway, very clear and easy to follow step by step for those who are fit in mathmatics. Thanks !

Very great appreciation for an "every effort made" thorough tutorial.

Tried other videos but hands down, this is the best out there. Thank you very much for explaining in a very simplified way. Hpoe you will make video on frequency response as well.

The way he explained is sweet and simple ☺️

This is THE MOST beautifully presented and explained video on Small signal analysis of BJT! Excellent, excellent job! A small request, can you please make a video of small signal analysis of Mosfet?

Nice video sir could you please make one on mosfet?

This was a great video. Thank you so much, I'm finally understanding this topic.

thank you very much, sir. watching your video i understood the small signal concept very well thanks to you. and i got to say you really are a good tutor please keep up the good work.

Fantastic explanation… thanks so much!

This vid is helped me alot in EE class

Great stuff, really helpful!

best video that explains every step

Excellent work.

the best video on youtube for ssa

Great Work!!

Great video, thanks a lot!!

Excellent job! Thanks so much :)

Out standing video sir. I am subscribing your chanel right now

Amazing video, very good explanation!

I am literally paying $27k per semester (less than 4 months) to learn this. And my class isn't as clear as this.

I don't have word this is great

Really great video. Hope you can add more video about Circuit!!!!

great content good sir, thank you.

Thankyou so much for this

Best video out there

Thank you 💓

Thanks a lot!

You could make life a lot easier by making use of the concept of the dynamic emitter resistance, that is the slope of the Vbe vs Ie curve. It is equal to the reciprocal of gm and depends only only the emitter current and the absolute temperature. At room temperature, it is simply 26mV/Ie (sometimes taken as 25mV/Ic), so should be immediately calculable from the dc analysis. Now see how it simplifies the calculations and makes them more practical: At 15:22 "So we feel pretty happy with this result", referring to Av = -β.Rc/rπ, but that looks to all the world as if the voltage gain depends on transistor β, which it doesn't. In fact rπ is just equal to β.re. That is logical since rπ is just the slope resistance of the junction seen from the base, and the base current is β times smaller than Ie (for any modern small signal transistor, β >> 1 and Ic = Ie). So Av = -β.Rc/rπ can be simplified to Av = - (β.Rc) / (β.re) = - Rc/re which is a much more usable result and shows that the gain is independent of the transistor parameters. In fact, Av = - Rc/(25mV/Ic) = -Ic.Rc/25mV. It should be obvious that as Ic.Rc is just the quiescent voltage across the collector resistor, the maximum voltage gain of a common emitter stage is necessarily limited by the supply voltage alone. If you want the output to be able to swing symmetrically without clipping, then the collector bias point will be about half the supply voltage (Vs) giving a maximum possible gain of Vs/50mV. Similarly, at 30:28, you have Av = -(gm - 1/Rf).(Rc || Rf). If we write the ratio Rc/Rf as FB - a feedback ratio which gets smaller as Rf gets larger - we can simplify Av as follows: Av = -(gm - 1/Rf).(Rc || Rf) = -(1/re - 1/Rf).(Rc.Rf/(Rc + Rf) = -(Rc/re - Rc/Rf).(Rf/(Rc + Rf) = - (Rc/re - FB).(1/(FB + 1)) So if feedback is very small (Rf >> Rc) then FB = 0, and Av approximates to - Rc/re as is the case without feedback. If feedback is larger, so that Rf = Rc, then Av = - (Rc/Re -1)/2 or about half of the gain without feedback. Those are useful results.

LOVELY , THANK YOU

thank u so much Mark

excellent !

at 13:40 on the video, for Voltage gain, The resistor R pi is basically (Beta)x(re), so the beta's will cancel and you will get Av= -RC/re re = 26mv/IE

This is amazing 👏🙌. May you please do the same with MOSFETs as well.

I love you MARK!!!!!!!!!!!!!!!!!

Excellent explanation of bjt small signal analysis. I really loved the way you teaching A small request Sir Please make a video on Mosfet

Thank uu soo much ♥️♥️♥️♥️♥️♥️♥️♥️

thanks sir you are the best

thanks

Btw perfect lesson, thanks a lot!

We short circuit Vin for measuring Rout as there is a voltage source of Av*Vi in internal composition of the right part of the two port :)

Hello Mark, Your videos are very usefull. We miss you and your lectures. Would it be possible to get more please? Regards

As perfect as they get 👌✌️

That is awesome Sir. You made things simple and vivid clear. But I have been desperately looking for current gain(hfe) expression in this hybrid pi model(the second one with feedback resistance rf, in my case it would be Rbc). Could you pliz explain that part too? Thank you.

Great cool

Mr. Mark : Why are the input signals shown with a +/- in the a/c analysis circuit? I have seen them in some text books also. Regards.

Many thanks for these lucid presentations. Where can I buy your book!? One thing still hurting my head: you say at the start 'the dc power supply looks like an infinite capacitor', so you short-circuit it. But the a.c. input signal is never travelling north towards Vcc, so never going to ground via the power supply cap, so...??

i love you

What I dont understand is why does the current i_c flow through R_C and not directly to ground at 11:55 ?

If someone can help me understand the first AC equivalent circuit I would greatly appreciate it. I'm a little confused as to how RC and RE can be said to be in parallel. To me, it would appear that from an AC perspective, shorting the power supply appears to shunt everything out of circuit except for R1 as the entire side of the circuit up to what was the collector side of R1 would have to be at the same voltage potential. To my limited understanding, this AC circuit would simply look like R1 is one branch, and the other branch is a parallel connection between R2 and RE if the transistor is on. It just looks like the series combo of RC and RL would have the same potential at both ends so there could be no current flow through them

Wow, this was great! But I've some naive doubts. • how can the transistor run on a small signal, without any biasing? Or Do we primarily assume that the transistor is running at some voltage ?

This video is very clear! But why is the current source connected to ground at 23:08?

much worth then any other transister lecture.

hi do you have common emitter for pnp ? im really struggling with my assigment as so many good tutorial are for npn and not pnp :(

35:35 If the circuit has L parellel R --> Rout=RL? Right?

Amazing video, very good explanation! but am quite naive on how did you know the direction of If in 24.42. Thanks if anyone can be of help also

the equivalent =re model

4:18 "the ac sauce that's driving the circuit"

may i ask on the last circuit why do you ignore the fact that r pi is in series with rf?

26:40 how did u find( vout-vin)/Rf

fancy making one on mosfets??

At 21:12, when the current source iC is = to 0, why is it not replaced by a short circuit?

If you take the expression for Vout = Vin you got from the nodal analysis and apply it to the second expression you got from the mathematical tools. would that still be correct?

22:05 all the time, every time.

is this pi model?

My professor was talking about calculating DC Bias before we get to the AC part. could you explain what exactly that means?

I'd contend that the transistor symbol should not appear in the ac circuit but be replaced by its ac model immediately. That'll prevent the mistaken belief that a 0.7 V still exists across the base-emitter junction.

What happened to the r_o in the hybrid pi model?

Nice video sir but i have a small doubt. Can't we write i1 as (ic+iF) 25:35 using KCL?

why 1/Rc + 1/Rf = 1/(Rc//Rf ) ?

What's "Small-Signal"?

How can i find the value of the r π of a BJT transistor? Is it written in the datasheet?

This analysis is fine as long as the output voltage swing is very small compared to Vcc , ie around one tenth of it . But once you try to have a bigger swing in the output, the gain will vary tremendously, and the output signal will get deeply distorted. These lectures may be good as a starter, but not in the real world. If someone wants to know what is in the real world, see this lecture and enjoy 🙂. kzfaq.info/get/bejne/h594l7ylmLyre4k.html

what is the point of this? Does anybody do this in practice?

You should provide simple Videos, based for poeple who have never studied on Universities. You are presenting only yourself. People who are familiar with it don't Need this Video anyway. The stars on KZfaq are People, who are able to explaing complex Things in a simple way.

Thanks 🙏👍💯😊