How Transistors Work - The Learning Circuit
Вставка
- Опубліковано 7 лют 2025
- 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
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 👍👍
In just 7 min you cleared every thing. Teaching is an art and that's true.
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.
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.
This is an AWESOME lesson. You pulled back the veil that has shrouded this in mystery to me for years.
Just a small correction.
It is called bipolar because it depends on both electrons and holes! not because it has 2 pn junctions.
Excellent video.
Easy to understand. Logically ordered.
Very professional.
Like listening to a talented engineering expert.
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
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!
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
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??
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 think this is the first time I've ever been able to wrap my head around this.
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....
You have the most perfect explanation about transistor using precise circuits
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 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
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.
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 !
Thanks sister. U explained every thing in a very understandable manner.pl extend your lesson further for novice and other interested.
This is the most amazing explanation of transistors that I have ever run across! Thank you!
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 explanation
Amazing teacher!! Please keep up the good work 😊
This is one of the top electronics channels out there
With a non-science backgorund was struggling to get a minimum jibor-jabor explanation. Thank you so much
This lady is really cool, Im binge watching her tutorials. Excellent teacher !
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.
good one...simple & effective
excellent teaching Karen...Thank you!!
Excellent description & thanks
I like your style of teaching...
Best explanation i found thus far
You 'v got me on the right way, of the transistor. Thank you very much Karin..aptly great channel.
one of the best explained ....thank you so much...
thank you so much for simplifying the lesson😀.
Best explanation I've heard so far, thanks.
Very nice information and presentation.
OMG, thank you Karen.....a lot easier to understand than some of the stuff I've read!
Comprehensive, easy to understand explanation. Thank you.
Very nice 👌 thanks for educating the world 🙏
Very well explained
amazing, none of UA-camr can explained except YOU, thanks
Wow, this is amazing you deliver it in a unique and short way. Thank you, god bless you.
Hi, how are you.
I am really flattered. You explained very nicely and impressively.
I am 60 years old man with 42 yeas experience in technical work and I have many
Invented designs and many mega projects but I am living in the environment
Where is no support from the government for the real visionary people.
Each day I am thinking that life is not to waste and each breath is to find out the
Real good way to facilitate the whole mankind, but the people who has
Power but they don't have a good visionary mind.
If I were sponsored by the hogher level authority, I am 100% sure that My only
One development program can bring wealth to the whole world but,
I am helpless to show because there is no support and sponsor for the true visionary mind people.
I am very much impressed from your ability to explain and
the real
Seekers.
Love you so very much, ❤ may God bless you.❤❤❤
Please also explains about voltage amplification & modulation by using PNP & NPN Transistors
terima kasih puan. Moga Allah sentiasa merahmati puan
You simply the best.easy understanding how actually transistor works.
Very nice way to lecture. Understand easy
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)
Amazing presentation, deep but easy to learn.
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.
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.
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
Incredibly clear explanation. Thank you.
Great Video Karen! Amazing explanation and easy to understand
Thanks, professionally made and good for reviewing the fundamentals.
Beautiful concise explanation!
never seen such a well explained topic
The way in which you are teaching is lajavab
Hi, I'm Tareq from Bangladesh. Thanks for your nice concept.
Now that's an effective way to teach, great stuff, thankyou
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.
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.
Excellent explanation and very nice explanation. Thanks for the tutorial.
Excellent information, many many thanks, I have learnt alot.
Fast explanation for this novice, but upped my transistor knowledge by 80%.
Very nice explanation
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!
the best transistor tutorial.
Great intro to transistors!
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.
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?
Thank you Karen! You’re awesome
Freaking awesome video, really dispels the difficulty of learning this stuff!
Super learning circuit man
Very informative video
Thanks
Awesome video.. amazingly useful..! Million thanks for sharing..
great explanation!!! Thank you for sharing your knowledge!!!
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!
Thank you so much for this explanation, solved a problem after a month
Darlingtons are an awesome solution for interfacing micros with stepper motors; done that a few times in the past.
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
Well explained, great work
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.
Lovable teacher.
very nice teaching
I came to an understanding that I have viewed an good explanation of the working of Transistors. After reading the comments of viewers , I am back to square one.
explicit, well presented and made easy.
very good and detailed explanations, cleared so many doubts which i had about transistors. thanks for making this video.
Thanks so much .. this is a great video to understanding npn and pnp transistors .. really thank you 😊
HOW TRANSISTORS WORK THE LEARNING CIRCUIT:---
DEAR YOUNG LADY INSTRUCTOR,
Watched yr above video and felt fortunate to come across this valuable video and yr imposing tUtoring and lectureing capabability.
At the end you asked whether the listener has any questions and please listen to my reply.
1. Video very very useful to learners.
2. You taught the above subject very well and you are a gifted teaching instructor
3. Video visuals/circuits and detailed tutoring compilation very well planned and executed.
4. Yoy spoke in OXFORD ENGLISH With which we are conversant and so could grasp easily.
5. Clear audible voice and clear pixture visibility
6. Speaking pace slow and study enabling not to miss any by slow learners like me.
7. Please contunue to teach and dont look back as many learners are eager to watch and learn
8. Your grasp of electronics is sound and shows yr experruse in the field. And i hope you will make many more videos on electronics including digital electronics where transistors play a major role.
AND LASTLY THANK YOU YOUNG LADY AND DONT FORGET TO POST THEM TO ME.
Vatsa BANGALORE INDIA
except the explanation for the PNP transistor is not correct. We would apply .7v across the B-E to bias it on. PNP & NPN both require only .7v to turn them on.
And this is Americsn English, not Oxford by about 3,000 miles.
very helpful I would have to have practical applyications before I can get it in my head Thank you!
Very useful tutorial
it's very use full video thanks
*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.
Excellent very well explained
Very good teaching, thank you.
This video has taught me more than any other video. Thanks 😊