Sir! I want to repeat this everyday: You are the best Electronics teacher in the whole world. Thank You very much!
@stuartbruff8786
4 күн бұрын
The conventional viewpoint has bugged me for years, so it's nice to see someone articulating what I'd thought all along and caused me a lot of self-doubt. Nice summary.
@whatzause
Жыл бұрын
I've done a lot of work in electrical circuits, but thanks to you, today I found out (basically) how an air-conditioner works! Very simply explained. Thanks!
@flurng
7 сағат бұрын
As Bob so astutely pointed out, in order to get any measure of linearity from the input voltage variation, it must indeed be restricted to a very small operating range. This, combined with the highly linear relationship between base and collector currents, is quite probably why "they" say that BJT's amplify current, rather than voltage . Yet, I have always felt that this highly restricted input voltage range is the VERY REASON they are so useful as amplifiers, since this is PRECISELY what devices such as dynamic microphones, magnetic pickups and phonograph cartridges provide! After all, if they REQUIRED a much wider input range, something more on par with the output voltage range, then their gain would be rather insignificant, and thus, their usefulness as amplifiers would be greatly diminished!
@charlesschneiter5159
Жыл бұрын
Thanks for this latest refresher! You are a teacher of great talent 👍
@michaelmccarty4765
Жыл бұрын
Very, very helpful! I'm a vacuum tube guy trying to understand transistors, be them a BJT, FET, JFET, MOSFET... and the others. I've never heard BJTs described this way before. It's a lot of food for thought. Thank you!
@tvamos73
5 ай бұрын
My teacher told me that if I can imagine the BJT is a current controlled current source and MOSFET is a Voltage controlled resistor.
@flurng
4 ай бұрын
Another terrific explanation, Bob! Yet, if I may offer a different point of view, the way I always understood it, is that the base-emitter (input) current directly controls the collector-emitter (output) current. Thanks to Ohm's law, increasing base voltage causes a rise in base current, which in turn, raises collector current far higher. Finally, thanks again to Ohm's law, this rise in collector current causes a substantial drop in collector voltage. And, conversely, dropping base voltage would have the opposite effect on collector voltage! (P.S. - I should point out that this explanation applies specifically to common- emitter circuits!)
@OmarMohamed-ej5ek
Ай бұрын
Wow thank u teacher to remind me the relation between current and voltage on bjt
@biseraciric454
19 күн бұрын
Thank you very much for this explanation! 👋🏻 😄
@LISANCACOM
8 ай бұрын
Thanks, really informative, clear and educative video.
@jnc5255
8 ай бұрын
Thank u sir for great explaination keep up the good job and godbless
@patricklanra3507
8 ай бұрын
A very informative video - Thanks Sir
@ChrisHalden007
Жыл бұрын
Great video. Thanks
@klmkt4339
6 ай бұрын
In the world we should value and look for linear relationship. What i learned from transistor
@michaelwise9363
2 ай бұрын
Do you have video for an rf npn amplifier (eg BFQ19) where a choke is used in the supply to the collector? How does this effect things? Thanks M
@jonahansen
5 ай бұрын
Short answer: Because that's how they work. There is always a relationship between voltage and current, and the operation of a BJT is best characterized by the current relationship.
@Donquixote-qv7sp
Ай бұрын
Wait..so in actuality the VBE voltage is the one that controls the current ......
@Coolgiy67
Жыл бұрын
How does it actually amplify the current? Maybe you can use the hybrid pi model to explain ?
@mikesradiorepair
6 ай бұрын
This is probably a oversimplification but here goes. The collector has a voltage applied to it. The emitter in the video example is tied to ground. The collector to emitter basically looks like a infinite resistance with no base voltage. Applying a small voltage to the base allows current to flow through the collector to emitter. The higher the base voltage the higher the collector to emitter current. So in a nutshell, the small variable base voltage controls a large collector to emitter current. Mike KC3OSD
@flurng
4 ай бұрын
Not to get into the whole "Conventional current vs. Electron flow" debate, but the truth of the matter, is that electrons flow from negative to positive. So, with an NPN type transistor, as shown in the example, electrons actually flow IN to the emitter. From there, due to the atomic structure of the semiconductor layers, approximately 5% of those electrons flow OUT of the base, while the remaining 95% flow OUT of the collector. This proportion is maintained regardless of how many electrons (thus, how much "current") are actually flowing at any given time. As a result, a small change in the base current creates a much larger change in collector current, thereby amplifying the current.
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