How Transistors Work - The Learning Circuit
HTML-код
- Опубликовано: 20 сен 2024
- Rather than using a physical, mechanical switch, a transistor can act as an electronic switch, using signals to turn it on or off. Karen goes over what transistors are, how they work, and some different types of transistors: Bipololar junction transistors (BJT), NPN transistors, PNP transistors, and darlington transistors. Connect with Karen on element14: bit.ly/2EASjxT
Visit The Learning Circuit: bit.ly/2OIkbEQ
Visit element14 presents: bit.ly/2PNXo7d
Visit Project14: bit.ly/2PPrjfk
Previously, we’ve talked about how diodes work. Silicon diodes have a p-n junction. Bipolar junction transistors or BJTs are bipolar because they have two p-n junctions. BJTs are essentially two diodes in a single package. The two main types are NPN and PNP transistors. NPN transistors have two n-type regions on either side of one p-type region, while PNP transistors have two p-type regions, on either side of one n-type region. Bipolar transistors have 3 leads, one going to each region. Typically, the middle layer is the base. P-type in an NPN, and n-type in a PNP. One of the other layers form the emitter and the third, the collector. These are labelled B, E, and C. On the circuit symbol, the arrow is always on the emitter, so we can tell which lead is the emitter and which is the collector by seeing which one has the arrow. The NPN transistor symbol has an arrow on the emitter pointing out, while the PNP transistor symbol has an arrow on the emitter pointing in. Transistors act as an electronic switch, conducting current across the collector-emitter path when a voltage is applied to the base. The switch is off if there is no base voltage present. When base voltage is present, the switch is on. We know from our diodes lesson, that diodes require a forward voltage of 0.7V before they are turned "on" allowing current to flow. In a standard NPN transistor, when 0.7V is applied between the base and the emitter, the transistor “turns ON”, allowing current to flow from the collector to the emitter. With an NPN transistor, we normally bias the device so that the collector voltage is positive with respect to the emitter. The voltage across these two points is referred to as the Collector-Emitter Voltage or VCE. If you connect the base to be positive with respect to the emitter, the voltage is referred to as the Base-Emitter voltage, or VBE. For a PNP transistor, rather than needing a minimum of 0.7V on the base of the transistor, there needs to be a minimum difference of 0.7V between the VCE, collector-emitter voltage, and VBE, base-emitter voltage. If the circuit power supply is a 9V battery, the base-emitter voltage would need to be no more than 8.3V for the transistor to turn “on” and allow current to flow between the collector and emitter. If the base-emitter voltage is 8.6V, a difference of 0.4V, the transistor would be off and no current would flow. If the base-emitter voltage is 7V, the difference of 2V is greater than 0.7V so the transistor would be “on”, allowing current to flow between the emitter and collector.
This content has been recreated as an eBook for easy offline reference - part one is available now for free: bit.ly/3tpT0PS
Also check out the Candy Thief Alarm project Karen created with her newfound transistors knowledge bit.ly/3jlR32f
Or the conversation between Karen and James (aka thebaldengineer) about transistors bit.ly/36HoGXr
Hey, your ebook link doesn't appear to be working :/
element14 presents, go to hell.
You literally taught me in 7 minutes what my instructor failed to do in an hour.
You too fast
This is an AWESOME lesson. You pulled back the veil that has shrouded this in mystery to me for years.
I swear to god I just spent 15 minutes reading about how transistors work but 3 minutes into this video I feel a lot more enlightened. The article never even mentioned why it’s called a transistor.
Maybe check the first thing she says at the :25 mark
@@bradzimmerman306 how does it feel to be stupid?
@@entidade1000 I don’t know. Tell me how you feel.
Excellent video.
Easy to understand. Logically ordered.
Very professional.
Like listening to a talented engineering expert.
I think this is the first time I've ever been able to wrap my head around this.
Thank you for this video. Well explained and easy to understand.
You are the personal teacher of so many people that acess youtube.
You give joy, and self fullfilment to so many people. I cherish you in my mind.
I've spent the last week trying to figure out transistors, reading a lot of material and this was one of the most helpful resources in understanding them. Thank you so much for sharing!
Me too
Expecially for the PNP
I am a new learner and found this video very useful and informative. The pace was perfect for me.
what is your progress at the moment??
5:22 so for PNP: does it means if there's only VCE closed circuit connected to PNP without VBE circuit - will VCE works? (Since 9V - 0V > 0.7V)
There is an error here for PNP, I think, it is still VBE that should exceed 0.7 V (or, more accurately, should be less than -0.7 V, i.e larger than 0.7 by magnitude). If you think about each np junction as a diode, it is just a direction that changes in pnp but still same voltage to start moving electrons/holes across the BE junction, not that you suddenly need VBE close to VCE (determined by external conditions !)
Great refresher. I used to dabble with semi conductors as a kid, but didn't really understand how they worked. This video brought it all back for me...thanks!
Thanks, this is the only video that makes it super simple to understand without the presenters stroking their ego by trying to sound smart by overcomplicating things.
2:38 is this supposed to be stated as 'while a signal current flows from the base to the emitter'? as opposed to flowing from the base to the collector?
Just a small correction.
It is called bipolar because it depends on both electrons and holes! not because it has 2 pn junctions.
PNP = Points iN Permanently
NPN = Never Points iN
this may help with reading schematics.
i remember this in class.
wow.. really helpful
Excellent MNOMIC Andreas, if you have any more; indeed if anyone has any more, please leave us them in the comments. They are really helpful. Thanks, hats off to you and cheers.
Thanks Stevens
Andreas. Thank you. This was the question raised in the mind when i was listening the lecture. How to keep in memory the arrow direction.?..you answered. Thank you
Thanks to your simple explanation i think i finally understand PNP transistors which seemed more complex than NPN :D
So then for a PNP example you give, the base-emitter needs a power supply of at least 8.3 volts or you wouldn’t be able to shut the transistor off? Does this mean that if you were using a microcontroller that is only capable of emitting 3.3 volts, and you wanted to use one of it’s output pins as a base emittor, to a transistor powered by 9 volts, you could use an npn transistor, but not a pnp transistor?
This is the most amazing explanation of transistors that I have ever run across! Thank you!
Mam namaste
If possible please make videos on IGBT working principle 🙏
Correct me if I'm wrong but at 4:43 when describing the the pnp BJT, shouldn't it be maintained that Veb >= 0.7v ? The equation stated says Vce - Vbe >= 0.7v which is the same as Vcb >= 0.7v
Rascul It should state that Vbe
Yes, something is wrong here. If I take 2SA1015 max specs it says VCE=-50V VEB=-5V, running it with emitter at 18V and collector grounded as I do, I would not be able to shut it off at all, if the formula in video is correct, since I can never bring VBE close to 18V (I'll leave sign convention out of consideration here)
Will we see transistors used in a circuit in a future episode? This information is great. I haven't had much exposure to working with transistors so I'll be sure to review this video back couple of times to make sure I understand everything.
Yup! Coming up next Wednesday! I usually do episodes in pairs, first a lesson video, followed by a project using what was talked about in the lesson.
Please also explains about voltage amplification & modulation by using PNP & NPN Transistors
Thanks, professionally made and good for reviewing the fundamentals.
i finally felt i understood the transistor basics now. wow that took some years to grip but this video confirmed everything ive understood and by watching this i now got it, thanks
Amazing teacher!! Please keep up the good work 😊
it is a great Explanation. when somebody explainsa this way Electronic circuits become easier to understand. I'm a beginner. Thank you very much.
Excellent video but a bit hard to follow on its own, without looking at the "previous video" you refer to. I'd suggest providing a link to it for ease of use. Cheers!
BEST EXPLANATION..., I TRULY HOPE THIS CHANNEL CAN GIVE ME A BETTER UNDERSTANDING OF ELECTRONICS AND HOW THEY ALL WORK TOGETHER THANK YOU I WILL BE SUBSCRIBING !
OMG, thank you Karen.....a lot easier to understand than some of the stuff I've read!
you are heaven sent.... Got D's and E's in physics bt now that i need PCB skills in real life you make it much much easier... thanks
Without really knowing much of anything about electronics I could still get the idea of how this works. Fantastic....must resist temptation to binge watch entire series now....
4:20 This is incorrect for the diagram you've given. You will only loose .7v from the circuit if your collector and base junctions are supplied from the same source. In your diagram you'll only loose about 50mv (Assuming a 2n3904 and 1k load with some amount of base resistance) in the collector to emitter channel as you are supplying the base current separately from the collector.
I caught that as well. the Vce is (Vcc-Vrc)/R1 - Vled = [(Vcc-(Ic*R1))/R1] - the Vled drop from the LED not the .7v from the Vbe. Also BJTs are current controlled not voltage controlled. She is explaining the switching effect as if they are JFETs or MOSFETs.....which are voltage controlled semiconductors. Try applying 7v to the base of a BJT without a resistor to limit the current flow and watch it burnout instantly.
we owe everything to these transistors. I was working as a tube tech when these devices started to hit the market. like in all things the new replaces the old. as for npn and pnp it depends on the circuit I design. thus, a super stable low frequency tunable osc requires a small load transistor in a reverse polarity configuration.
Comprehensive, easy to understand explanation. Thank you.
You have the most perfect explanation about transistor using precise circuits
Thanks sister. U explained every thing in a very understandable manner.pl extend your lesson further for novice and other interested.
In just 7 min you cleared every thing. Teaching is an art and that's true.
good one...simple & effective
excellent teaching Karen...Thank you!!
Wow, this is amazing you deliver it in a unique and short way. Thank you, god bless you.
You simply the best.easy understanding how actually transistor works.
This lady is really cool, Im binge watching her tutorials. Excellent teacher !
Excellent description & thanks
Fast explanation for this novice, but upped my transistor knowledge by 80%.
Excellent explanation
This video has taught me more than any other video. Thanks 😊
It's a full information video thank you so much for I hope in future you will make more video same lake that for us may god bless you
Very nice 👌 thanks for educating the world 🙏
If you discuss Darlington Pairs, it would also be useful to discuss Szicklai Pairs. I understand that the Darlington Pair discussion was a teaser. Therefore, I suggest a follow up in depth discussion of Darlington and Szicklai Pairs for a future video.
Hello, first time I find a girl who works in the field of electronics, I am happy For watching your wonderful channel, greetings to you, my dear sister Very nice 👍👍
I learned vacuum tubes first and some of the older books compare a tube to a transistor. So that made it easy for me to learn transistors.
Tubes were much nore forgiving. I began designing tube circuits and if you make a mistake like grounding a grid, the plate glows cherry red hahh
With a transistor, it just gets damaged and the circuit fails to operate leaving you with "ok why isnt this working?"
Of course working with non lethal voltages has its benifits hahah
Once I was working on a T.V. and had my hands inside while adjusting the time and my knuckle came to close to the horizontal output tube playe cap. That Hurt a LOT!!! I once got belted with the anode wire for a b&w crt. my jand felt like it was in a. Vise and then got smacked witha hammer! Ouch!
@@rty1955 I've worked on both. Transistor sets you slip with you probe and short something and you blow out half the set.
@@cat-lw6kq haha true. Ya gotta be careful with all.esp. now with close tolerances. Gone are point to point wiring where U can push components out if the way to get to a test point
@@rty1955 those old tube sets could take a lot of abuse. My teacher would show us what would happen if parts of a tv failed by removing tubes in a working set. The set was powered on and he would pull tubes one at a time. Try doing that with a transistor set.
@@cat-lw6kq how very true. He must of had silicon hands! I recall working in a broadcast T.V. studio where 21" Conrac monitors hung from the lighting grid. They replaced the covers with a screen mesh to allow for airflow. When i took it down for repair, I put it on the bench and powered it on. I could have baked a cake in that thing!
Very well explained
I did mechanical and he did electrical. I got more interested in electronics and he helped me a bit until I couldn't catch up with him especially when he started designing power amplifiers using Darlingtons . Oh yes! I manually etched a working stereo 20x20W. That was in 1981 and now I can try catch up.
Incredibly clear explanation. Thank you.
4:25 shouldn't you account for the voltage dropped by R1 too?
Why 0.7 VDC EB voltage? Because of the material the transistor is made of. Silicon transistors require 0.7 VDC EB bias voltage to turn on. Germanium semiconductor components require 0.3 VDC bias voltage.
But now a days, Gallium Arsenide is used as strata, then what is Vbe?
I like your style of teaching...
Best explanation I've heard so far, thanks.
i did not quite get how the signal current flows,is it from base to collector OR from base to emitter
Thanks so much .. this is a great video to understanding npn and pnp transistors .. really thank you 😊
This is one of the top electronics channels out there
Amazing presentation, deep but easy to learn.
Excellent explanation and very nice explanation. Thanks for the tutorial.
This is DEFINITELY and EASILY the BEST explanation I've ever seen on this target level. Using those two voltage sources in the explanatory schematic was genius!!! And the explanation on vBE and vCE was something that often doesn't even get talked about in other vids.
except the explanation about the PNP is not correct. The only difference is the battery in the diagram it would be flipped around so the (-) goes to the base.
PNP and NPN both require .7v bias.
@@cat-lw6kq It looks correct to me. If using the classic positive current model then the current flowing from positive terminal on right flows into the emitter and (mostly) out through the collector, where the base signaling current would need to have a voltage of 8.3V or less. In other words, if you think in digital terms (rather than analog) she is trying to show that a logic 0 applied to the base switches the PNP BJT on to allow the primary current to flow through from E to C.
Suggest you buy one of those cheap transistor testers off ebay. for test some transistors with it, it will show the bias voltage and the gain. The tester has a digital readout, it shows bias (B-E) voltage and gain. You will see a bias of about .7v if the transitor is good.
It isn't the best. Half of it is totally incorrect. Look harder. Try the PNP circuit shown and measure for yourself. The voltages are not as described.
Great video. Really enjoying these. One small nitpick - at 2:39 I believe you really meant to say "the small signal current flows from the base to the emitter" not "from the base to the collector". The diagram however is correct.
Great
I just noticed that. I was like, "Am I misunderstanding??" Guess she just misspoke.
one of the best explained ....thank you so much...
Best explanation i found thus far
Freaking awesome video, really dispels the difficulty of learning this stuff!
Great Video Karen! Amazing explanation and easy to understand
Awesome video.. amazingly useful..! Million thanks for sharing..
Hi, I'm Tareq from Bangladesh. Thanks for your nice concept.
Thank you so much for this explanation, solved a problem after a month
Can you plz make a video on how transistors oscillates the current.
You explain very well, congratulations Teacher.
I'm french student and i manage in english. Can i have somes transistor's applications ?
Thank you for all and have a nice day...👍
Great intro to transistors!
never seen such a well explained topic
You 'v got me on the right way, of the transistor. Thank you very much Karin..aptly great channel.
Thank you very much i really like your videos very educating keep up the good work
Well. This video was very helpful! I thought to turn on an NPN transistor, I just needed to have .6v sitting at the base. Knowledge gap. Didn't realize it needed to flow through b to e. Its working now! Thanks
Good video but never mentioned the material /chemicals used to enable those properties in the 'doping' process.
Hi Karen. I don't know much about transistors. I watched several of your videos on transistors. I do like it. I want to build a small circuit that I think it's doable by using transistors. Make it simple, I have a light in a box which I cannot see the light lit inside the box. If the light dies I don't know because it is in the box. So, I want to use a led to indicate the light is still alive. I cannot install the led in series with the main load circuit because the load could be a heavy load. So when watching your transistor illustration I think it's do able with a transistor using the same power source so if the main current is not flowing then the led turns off but I don't know how to do it. Could you please show me how to wire it. A diagram would be very helpful. Thank you so much.
thank you so much for simplifying the lesson😀.
A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit
very good and detailed explanations, cleared so many doubts which i had about transistors. thanks for making this video.
How do you know how much voltage or current a transister can take?
With a non-science backgorund was struggling to get a minimum jibor-jabor explanation. Thank you so much
Can you please mention how can we physically distinguish between a PNP and NPN transistors
You can't tell physically, they're often supplied in identical packages. You need to look up the product code, or test it in a meter, or just try passing a base-emitter current and see which way around it needs to flow.
Very nice information and presentation.
Seems there is an error in the explication. The V(BE) has nothing to do with V(CE) and the Voltage drop on V(CE) is significant smaller than 0.7V if switched on! Example BC172 has 0,25V V(CE)@ 10mA I(C) and saturation.
explicit, well presented and made easy.
Nice video - the part where you introduce the PNP transistor is wrong, totally confusing > PNP is just the compliment of the NPN, just reverse the signs of all the voltages.
Very nice video Lady. Please make more simple explanation videos about electronic. Thank you so much
*BEST* Transistor tutorial I have EVER seen, I kid you not! THANK YOU!!!!!! :)
yes now you are really confused. the PNP does not need 8.v B-E voltage to turn on, it only needs .7v. Suggest you buy a $7 transistor tester on ebay and test some transistors. you will see that a good transistor has a b-E voltage of about .7v.
Good intro. I want to drive 12v LED from an Arduino which puts out 5.5v. I think this means I need an NPN transistor and an 18v VCE power supply. I still don't know what the R1 value is, but I think I am getting the basic idea.
I have made a video on this in my channel
I wish you were my university professor, because you just explained something better in 7 minutes than they did in 7 hours' worth of lectures.
Beautiful concise explanation!
at 2:39 "the signal current flows from the base to the collector" should be "the signal [really, input] current flows from the base to the EMITTER"
i am electronics & communication engg in indian railways.
thanks for nice videos
It would also be nice to cover the Szicklai Pair. Also, I would like to see Transistor types, like the 2N2222 and the ZTX749, discussed. So far, Transistor types look like alphabet soup with numbers.
Excellent very well explained
I get the 0.7 Voltage Drop across Base-Emitter... however, how come there's NOT a 1.4 Voltage Drop from Collector-Emitter, since that passes thru 2 PN Junctions?
The junctions are in opposite direction, one pn, other np, so in ideal stable regime between emitter and collector you have drop of 0.7 V on one junction and rise of 0.7 volt on the other
@@dmitripogosian5084 Thanks for explaining this... now, I also sometimes see an equivalent Voltage Source of 0.2V at this same junction... can't figure-out why