BJT - Small Signal Model Explained

In this video, the small-signal model and the small-signal approximation of the BJT is explained.
By watching this video, you will learn the following topics:
0:00 Introduction
0:53 The concept of Transconductance
3:26 What is Small Signal Approximation
9:30 BJT- Small-Signal Model
BJT- Small-Signal Model:
When BJT is used as an amplifier, the small-signal model of the BJT is helpful in finding the amplifier characteristics. ( Voltage Gain, Input and Output Impedance)
BJT- Small Signal Approximation:
The small-signal model if the BJT can be used when the input to the BJT is very small. (When Vin us less than Vt (Thermal Voltage)).
When the input is very small, then it can be assumed that the BJT is operating in the linear region of the characteristic curve.
And hence it is possible to analyze DC and AC signals separately.
The transconductance:
The transconductance is the measure of how the change in the base-emitter voltage gets translated to the change in the collector current.
Transconductance (gm) = ΔIc / ΔVBE.
Unit - A/V or Siemens
For the small-signal, as ΔVBE is very small it can be expressed as
dIc/ dVbe.
And transconductance gm = Ic/ VT
In this video, after the explanation of the small-signal approximation, the small-signal model of the BJT is explained.
This video will be helpful to all the students of science and engineering in understanding the small-signal model of the BJT.
#BJT
#BJTSmallSignalModel
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Music Credit: www.bensound.com

[@ALLABOUTELECTRONICS]

The timestamps for the different topics covered in the video: 0:53 The concept of Transconductance 3:26 What is Small Signal Approximation 9:30 BJT- Small-Signal Model

[@KuldipSingha-do9uj]

The hero we need 💖💖, seen a lot of videos , searched many books , wasn't able to grasp this, thank you so much, sir 👌👌👌🙏🙏🙏

[@mishram4446]

Hi! Thank you so much for this video. I though it was difficult to understand it at first but later realized it was my lack of attention. I understood small signal analysis after 3 semester thanks to this video. You earned my subscription and definitely liked and loved this video.

[@saiftahsin1791]

Best channel about electronics on internet .

[@asifmehmood4501]

I wast stucked at this model for three to four days , thank you so much for makinh it simpler.

[@Vnifit]

You're a legend bro! Thank you.

[@JJHanna]

Excellent analysis!

[@shreyasjoshi7796]

Wish me Best Luck for tomorrow's exam :)

[@ALLABOUTELECTRONICS]

All the Best !!

[@shellysingh1786]

Thank you sir...

[@sLSAIKUMAR]

clearly understandble

[@mohamadfahmi404]

Let say my circuit is control by 50Hz square wave at the Base, does small signal analysis is required?

[@poojashah6183]

The best video on BJT👌🏻👌🏻

[@shadon_official2510]

Great video

[@moustafashafik9221]

Very Clear and informative video. God bless you

[@kkumar5614]

Sir Can you please plz share the slide in description section or comment section, it will be easy for us to revise

[@charbelboumoussa3248]

i love you man better than my teeacher

[@SanKChannel03]

Thank you very much!

[@vinodsetiyar]

Hey, great videos! Can you please also make videos on Active load in BJT, BJT as a diode and Frequency Response analysis. Please!!

[@suyeshkumar6333]

Thnx for the hard work bro. Still appreciate your efforts.✌✌

[@mayurshah9131]

Excellent 👌

[@gyanganga8441]

Please provide these videos in less resolution show that we can watch more videos instead of one or two.👍

[@ALLABOUTELECTRONICS]

You can lower down the resolution manually in the video settings. Instead of 1080p, you may select 720p or 480p if required.

[@gyanganga8441]

@@ALLABOUTELECTRONICS I wanna below than 480p

[@Fantasticsman]

@@gyanganga8441 you go hell

[@abhay4147]

@@gyanganga8441 then watch it in 240p or 144p. But I am pretty sure you won't be able to see anything in those resolutions

[@anbu7406]

What is the actual meaning for del symbol?

[@abcddd580]

differentiation for a multivariable function.

[@vinaykumarkv5830]

Superbb👌👌🔥❤

[@mnada72]

Is there different small signal model for different BJT configurations like common base for example?

[@ALLABOUTELECTRONICS]

Irrespective of the configuration, the small signal model of BJT remains the same. Based on the configuration and the external resistor, the small signal equivalent circuit will be different for different configurations.

[@tomc642]

Well, I understand this small signal model, but the derivations just add complexity. I find the re model using a diode and controlled current source so much more intuitive. The diode ac resistance in the emitter is simply re=26mV/IE (the emitter current IE from the DC Bias) and the controlled current source Ic = alpha (Ie).

[@ALLABOUTELECTRONICS]

In some configurations, the analysis using re model is easy, while in some configurations analysis using pi-model is very easy.

[@tomc642]

@@ALLABOUTELECTRONICS Thank you, this must be the case.

[@sbybill3271]

@@ALLABOUTELECTRONICS do you have a video on re model as well?

[@munnapuppala1833]

bro 3:53 sec why did u take delta vbe very small?

[@ALLABOUTELECTRONICS]

Since it is a small signal analysis,so it has been assumed that the time varying ac input signal is very small in magnitude. And because of that the change in vbe on top of the Vbe is also very small. I hope it will clear your doubt.

[@munnapuppala1833]

@@ALLABOUTELECTRONICS ya bro thanks alot🤗

[@syedjaffar4963]

Which text book you have followed or referred?

[@ALLABOUTELECTRONICS]

You can refer Microelectronic circuits by Sedra/ Smith for this particular topic.

[@omerfarukcin3978]

@@ALLABOUTELECTRONICS I also used this book, but I hadn't understood it like that before :)

[@rajaramyadav7546]

@@omerfarukcin3978 yes I am also using same book But it is little bit confusing to understand.. It take a little bit more time to understand properly...

[@aristotle8777]

bhai aap pakistani hai?

[@JasonPwnsAll]

What is that symbol with the angled arrow and circle around it? (Sorry still new to this)

[@ALLABOUTELECTRONICS]

It is the symbol of BJT.

[@NKAVURUGANESHSIVAKUMAR]

Well,,. U may not need to draw that Circle around it... But the direction of arrow represents the Emitter... Downward Arrow represents the transistor is NPN Upward arrow represents The transistor is PNP