Tutorial: How to design a transistor circuit that controls low-power devices

[@mateo77ish]

I’ve watched dozens of transistor vids looking for exactly this info and none of the others put it so plainly and comprehensive. Thank you.

[@brianmcdermott4139]

I've never watched a video that was as informative and clear. Your explanations are complete without getting overly complicated. Thank you so much for making these.

[@DupczacyBawol]

PNP transistors especially, or transistor power that is used a little to warm up the transistor, so using Ohm Law is not 100% accurate :P.

[@danmick8645]

your comment makes no sense....wanna take another run at it?

[@flyjamaicanz]

lol......great video mate, very well explained.

[@glennsprigg2378]

"Power used to 'warm-up' the transistor" ?? The .7V loss through the Base/Emitter calculation, is a bit more complex than, but 'like' the typical .6V loss through a forward-biased diode. At such 'PN' junctions, the 'P'-type having a deficiency of Electrons, and so having 'Free-Holes'. The 'N'-type has an excess of Electrons ! (I'm keeping it simple here...). Now where they are physically touching, (and no voltage applied), for so many atoms thick in the lattice some of the excess flows into the deficiency, creating an Insulating barrier at the physical junction ! As a result, even when 'Forward-Biased' from a voltage source, a Diode needs at least about .6V just to break down this barrier, before it starts to conduct, so you will always loose this! A similar effect(s) are going on inside most typical Transistors. (Hence his '.7V' loss in his calcs). (1) For a Diode, this voltage loss is NOT dependent on the LOAD after the Diode! So for example, you could connect 5 diodes in series, for a precise 3V drop, or 10 in series for a 6V drop, irrespective of the load !! (2) This 'Insulating' barrier at the PN junction, can be considered the 'Dielectric' of a capacitor, so our Diode is ALSO a Capacitor, with the 'plates' being the P/N materials area themselves. NOW it get's interesting though!! as the higher the 'REVERSE-Bias' voltage across the Diode, this FORCES an even LARGER non-conducting 'neutralized' gap/barrier. 2 main things control capacitance.... The area of the 'plates', and the 'space' (dielectric) between them. So what do we have now??? A solid-state Voltage-Dependant Variable-Capacitor !!! Yep... and it is utilized a lot these days..... although now 'Special' Diodes are made to take advantage of this effect, called 'VariCap-Diodes'. Sorry about all that... :-) I just get 'excited' playing with software like 'Circuit Wizard', that allows you to design on screen virtually any electronic circuit including virtually all elect/electronic components & IC's, see it all run in REAL time, monitor ALL voltages & currents from ANYWHERE in the circuit simply by mouse movements. Not to mention auto creation of your PCB & all artwork when you are ready, with auto track routing. ALL before you touch your soldering (not the American 'soddering' :-) ) Iron. Have fun !!!

[@piskuljkopisljkuljkovic5294]

There are several components to learning electronics. One place I found that succeeds in merging these is the Gregs Electro Blog (check it out on google) without a doubt the no.1 course that I've heard of. Check out this amazing site.

[@ssl3546]

For 30 years I've seen explanations of how to use a transistor and never "gotten" it. Bravo this is spectacular. The best explanation of a bipolar transistor I have ever seen in any medium.

[@rajanne2947]

Very easy to understand you have a lot of patience! I obtained some extra insights by watching your exposition that with 20 years of doing electronics i was able to obtain today!

[@Burnitnow567]

Dammit, I wish the internet was around when I was in school!! You kids are sooo lucky to have all this knowledge available instantly! --OldGuy :)

[@gojohnnygo6869]

I've been thinking that for years. I wanted to understand and know how to do many things while in my youth but had no available quick easy answers like now. This guy basically covered a 50 page chapter in 20 min without going to the library first. This information would have taken most of a day to learn, if I found the right book. Having someone explain and show examples is so much better than reading about it. Kids these days have no idea how much easier it is to acquire information today compared to 25+ years ago.

[@j3s0n]

Humble boomer brag

[@christianam9951]

Yeah, but now they use it just to watch non educational stuff !!!

[@raybin6873]

C'mon now! Radio Shack had a "101 Electronic Circuits You Can Build " book you could buy...Healthkit offered radio controlling stuff (RC airplanes) and amplifiers...remember the ol' crystal radio? - I built one using thin lacquer coated copper wire, a simple crystal, a empty toilet paper cardboard tube, cheap low power earplug type headphones and a long piece of wire for antenna...it actually worked too..1965! (Crystal radio plans probably somewhere found on YT.) Aah yes..the good ol' days! Truth be - it's much better these days....so all you kids out there...you're spoiled rotten! Ha ha ha! 😉

[@daraa151]

Yead for my essays had to rely on library, when i go to library the book i want is already has been borrowed😏

[@docfoot316]

I learnt alot from this video ,well shown and explained ,and i am 65yrs and still learning ,Wish i had someone like this to teach me in my younger days .Many thanks .

[@AppliedScience]

When the transistor turns off, current flowing through the coil will cause a voltage rise on the collector. If the voltage rise is high enough to turn on the diode, current will flow through the diode and limit the voltage at the collector. The problem is that the diode cannot turn on instantly. It takes time for the diode to start flowing current. The capacitor smooths out the rising voltage, and gives time for the diode to start conducting.

[@pstark4]

Applied Science that part was curious, I was wondering why the diode feeds it back, wikipedia said it feeds the back emf back into the solenoid to lessen the change in current it experiences when turned off, love it.

[@yoramstein]

With the capacitor it make sence. But in all my life I never saw that capacitor to ground in Relay circuit. i red the use fast diode or low threshold voltage diode (Shotky?)

[@gondala]

schottky diode will just fine.

[@theoldbigmoose]

Your 5 volt input may have been solid between ground and +5v. I always put a 47K from base to emitter to deal with any leakage currents if the input is inadvertently left open, either by design, or by a failure mode.

[@figadodeporco]

amazing video mate! but, could you tell us what diode should we use for this clamp?

[@sfperalta]

Clear and well-presented. Amazingly, this circuit was pretty much the same as when I started studying electronics back in 1975, including the 2222 transistor! So for you younger students, the techniques outlined in this video will practically never become obsolete. We tend to think that the world is run on low-voltage, low-current technology (e.g. microprocessors, microcontrollers). But at some point real work requires higher voltages and/or higher currents, so studying transistor control circuits, like the one presented here, is very valuable knowledge.

[@JonathanAnon]

This video should be shown to everybody starting electronics... No talk of doping and PN junctions, show them this first so that they get a picture of what they are doing.. Too many electronics courses start at the microscopic level.

[@EdwinFairchild]

JonathanAnon because those courses are made for engineers . For hobbyists this is probably enough. For an engineer this is not enough.

[@jabl]

Even engineers would benefit of easier introduction to the matter.

[@curiosity551]

@@EdwinFairchild But the introduction at microscopic level kinda kills the interest in my opinion. I like to develop interest in something before getting started.

[@EdwinFairchild]

@@curiosity551 thats what i mean, if interest is the issue which implies a hobbyist, then ignoring the physics part of it is just fine. For an engineering perspective you dont have the luxury of interest, you NEED to know the intricacies whether they interest you or not.

[@deegee3142]

@@EdwinFairchild if you know it all, why are you here?

[@davidcohen9448]

Excellent video. Explicit, practical, logically ordered, easy to understand , in perfect English. Short-practical- utilitarian - easy.

[@calyodelphi124]

@2:54 Your description of the circuit symbols for NPN vs PNP BJTs is so ridiculously simple and intuitive @7:00 So THAT'S what hFE is used for with BJTs! This whole video is so informative it's helped me to make tons of sense of how BJTs work. You, sir, are a genius.

[@fabriziolavini7457]

I think i watched hundred of videos on the same subject. This is the first time that i see someone explaining every single step, all others always take those for granted. And abole all i appreciated the first part, when he described the several choices (possible components to use). All the designers make tutorials and never clear why they use a particular component among others and indeed they must know the reason (again take that for graanted). I congratulate and thank you.

[@ovidiub13]

I wasted weeks learning all you say in here, which I could have learned in ~20 minutes. Great video. Please add more tags to it, so you rate higher in search results.

[@ManyouRisms]

I have no business being here, however I stumbled upon it and watched it all the way through and I think i learned a thing or two along the way. You're a natural teacher, thanks s`much.

[@TheChangospace]

How I wish I had friends as smart as this guy in my circle. I love channels that pass along wisdom to others....thank you, Sir!

[@GaelicDrummer1]

Learned more in these few minutes than in the hours I spent on my own to clearly understand these principles. Many thanks and cheers from Florida.

[@szabonandi]

It took me years to learn this by myself when i was a young electronic enthusiast. You summarized nicely, and totally understandable. Great job!

[@saneeshelectronica9293]

See my vedio on transistor ckt design

[@webkris]

Just what I needed - Transistors are a simple yet madding concept that pushed me to look for a tutorial to get back to basics. Found exactly what I was looking for!

[@AM-dn4lk]

Why couldn't I have had you as my electrical theory teacher. What I learned in 21 minutes with you took me weeks with my teacher....and I probably still did not quite digest and assimilate it well enough. Thank you for your tutorials and lectures. You are educating the world.

[@kwgm8578]

Nice job. I was trained as an EE, and in the lab I blew up dozens of 2N2222 transistors. Later, as an "advanced" student, I destroyed a few Op Amps before I got the hang of their biasing. In the late 1970's, a simple NPN transistor was inexpensive - maybe 25 cents at the school lab stock room. Op Amps were much more expensive in the 1970's -- maybe a couple of dollars -- so I learned to read the data sheet carefully before breadboarding those projects. When in doubt, add a resistor! It's a good motto for any EE student or dabbler in the mysteries of electronics. One of the most valuable circuits a designer should know by heart is the voltage divider. Such a simple circuit, and so many fresh faces in the lab don't know it. Lesson 2, a little more complicated, is using a negative feedback circuit to automatically control current surging at the base and thought the transistor. Always protect your active components! I appreciated your trick to sink stored current around the solenoid, too. Thanks again. I'm retired and haven't played with electronics in a long time. I've been looking around KZbin for interesting channels. and yours is practical without being pedantic. I'm a new member and will be looking in.

[@felippesilva]

Good Tutorial. Thank you for that. Just another thing: You have to consider the power dissipation of the transistor itself, due to the voltage drops across it. taking the numbers (0.2Volts and 56mA), you can say that the transistor dissipates like 11mW of power, which is quite low for that circuit, but if you have a larger current and also a larger voltage drops on the transistor, you could damage your transistor if you don't attach it to a proper heatsink.

[@skullduggery6862]

I did exactly that and thought the same thing, I burned out transistors thinking they were defective by not using a resistor. This video shed some light on my life

[@richardmitchell5482]

First year electrical engineer student. Thanks for this video, I think you are a great tutor.

[@abdullatif9108]

I have searched the whole internet and the the things I was looking for are packed here in this 20 mins video .. excellent video

[@GarethJefferson]

So clear. So lucid. This is a great switching transistor 101. Thanks, really appreciate the work you put into this.

[@perspectivex]

I'm pretty sure this is the best introduction to how to practically use transistors and explanation of their essentials of how they work I've ever seen.

[@mariusgrobler]

Thanks. Your experience shows and this makes me feel confident about your lecture. As my brother says: in theory practice and theory is the same but in practice it's not.

[@AudioFanMan]

By far the most simple, complete non confusing and useful transistor lesson i have seen! Thank you... Subscription done!

[@Malorie001]

Very nice explanation. Super clear and concise primer on transistor basics. I was glad you skipped all the ohms law and such and just got right to the setup and calcs needed to drive your load. All the rest of the blanks can be filled in from innumerable other sources across the net. Excellent job!!!

[@maheshvinayaknerlekar3406]

So simple topic ..... But you inserted a universe of knowledge.... Great explanation.....Great love towards the subject.... Finally... simple topic is where the research starts... The world should know this.....

[@janussQv]

Best transistor tutorial I've seen yet. Thanks alot!

[@FeuFabricio]

I spent a few hours searching for a good explanation about this, and this video was the one who actually did it.

[@luismallozzi]

You are a life saver. Thank you for that explanation, it solved some questions that I had in my mind. It's nice to know why I am doing certain things instead of blindly following equations. Thanks.

[@gojohnnygo6869]

I went to school to repair PCBs many years ago but in my profession I wound up doing repairs at the next level. "Through that board away and replace it". This is usually the cheapest and quickest for repairs of most equipment but that takes all the fun out of it. I still enjoy dabbling with semiconductors but time is not on my side. This great video helped me to refresh the details I need for my dabbling. Thanks, Great video!!

[@m3thid]

This gave me the understanding I needed to figure out a circuit I was banging my head against. Thank you!

[@billgreen7283]

Don't damage the circuit with your hard head.....lol

[@frankvde8964]

Best explanation video on simple use of transistors in DC circuit so far...

[@northshorepx]

Thank you so much. I've spent ages trying to learn this basic theory and you have explained it wonderfully. I now feel I can grab some components and use them to switch real world items from an arduino. Fantastic video!!!

[@praveenkumar-vx3kw]

this is what i expect . most of the videos simply explain the low to high but you deeply gone. thanks a lots

[@PaoloTamburini]

Really a great video! Clear and simple! Thank you!

[@GianmarioMarchini]

cos è sta supercazzola? ...hai il dono della sintesi? me la riassumi? :)

[@PaoloTamburini]

La cultura non è per tutti!! 😜

[@GianmarioMarchini]

a hahaha....preparati per la stagione venatoria che siamo a brucio vah!!!

[@piehound]

Thanks for that lesson. I was a mere lad when most audio electronics were tube devices. And that includes TVs. But today i enjoyed upgrading my knowledge with transistors.

[@PropaneTreeFiddy]

Wow, great job on the video. I'm not too good with electronics, having learned strictly with MCU's early on and using digital PWM instead of actual power management. You have nearly tripled my knowledge on transistors and how they can be used, and for that, I thank you.

[@v2point0]

Same here :)

[@vincentbaelde-millar670]

Great tutorial. I know the feeling of blowing things up through a lack of knowledge: I destroyed two "5v" LCD screens instantly, it turned out the backlight was 5V, but the control was 3.3V.

[@ProtoG42]

You are a great teacher! Thank you!

[@bikashdas1182]

Perfectly done

[@fernandovelasco5632]

Just a curious question. Why is your current flow in reverse? Current flows from negative to positive

[@EdwinFairchild]

fernando velasco mathematically it makes no difference which way current flows. Most people use conventional current flow over electron flow

[@jonka1]

Yes it does but he is talking about CONVENTIONAL CURRENT FLOW where it is imagined that current flows from + to -

[@chandrakumargurung7034]

I ve deep interest in electronics i want to learn more...

[@SirMo]

When I first started in electronics it took me way too long to understand how transistors work. Wish I had this video when I first started. This pretty much covers everything you'd need to know about using plain BJT NPN transistors for use in DC circuits. Best and most concise explanation I've seen on the subject. Well done!

[@ironnerd2511]

Thanks for the great tutorial. I wish you would have given details about how to choose the appropriate clamping diode. Also a bit about the rol o the capacitor, and how to choose it. Also, it was unclear to me why NPN instead of PNP. I did not understand the justification.

[@vladan_kovacevic]

After many classes at University learning about transistors, this is where I actually understood how one works!

[@paulvoid3247]

Actually they DO make 4.3k resistors and they're part of the E24 series (24 values per decade).

[@Paulina-sy9cp]

You have a great talent for teaching. This video was so clear and easy to understand without you dumbing it down. You explained what to do and why as well as what not to do and why as opposed to so many videos that explain what to do without explaining the why. Thank you.

[@ryannicholl8661]

I would always use a MOSFET for power control, and not a BJT. Unless I needed to control the amount of current through the device. BJTs drop voltage and waste power.

[@stanimir4197]

Absolutely. Although MOSFETs have to be driven hard(er) for higher voltages - and even in this case, they would require a pull down resistor at least (5V is high enough gate voltage for most cases to driver 12V). It's harder to explain.

[@RexxSchneider]

A BJT is a perfectly reasonable choice for currents up to 100mA as the voltage drop and power wasted is then negligible. Above that, a logic-level power mosfet is a good choice, and essential if you have a 3.3V microcontroller. Remember that the mosfet will normally cost three times the price of a small-signal BJT.

[@renakunisaki]

I've been unsure about how a transistor is actually used for so long and nobody could really explain it, but this answered all my questions!

[@MatterLabz]

Back in 1979 my high school electronics teacher taught us to remember NPN = the arrow "Not Pointing iN".

[@no_one1073]

It's still the best way to remember it.

[@aenigmaticus_ca]

I'm only half way through the clip, and I have to say: thank you for teaching me the difference between NPNs and PNPs! Also clears up as to why my electronics project failed, as I was not given the distinction that they are different and as to what the difference is. The irony is, it's simple! I guess the teacher needed a break.

[@SianaGearz]

Starting with the age of about 16, most education systems require a bit of own initiative to acquire knowledge on their own on the part of the student (like at least asking questions in case something isn't entirely clear), as that is really considered the most important task of mandatory education, rather than simply conveying knowledge. But it might not be the case where you live, which begs the question, how would that kind of school system prepare people for college or university at all?

[@hignaki]

"Yeah but I live in a voltage world how do I get this solenoid to turn on and off" Legit LOL'd.

[@willie_mccoy]

Livin' the voltage life.

[@leachim66]

over 8 years later and this video is still one of the best practical examples of BJTs

[@michaelwasiukiewicz2620]

REALLY good video. Probably the best transistor video I've watched. Nice job!

[@dennisk5818]

I worked with EE's. I have some electronic background, but not design. I would marvel at my EE throwing together a complex circuit and wished that I had a fraction of this skill. This video is a great first step at understanding design, beyond just following a schematic. Thanks

[@CYBERlite2010]

Finally, a way to control a motor requiring 12 V from an Arduino and L293D. :)

[@KiwiMaker]

Awesome video thanks! just got a transistor working for the first time ever.

[@nickwalker5115]

Absolutely fantastic tutorial!

[@johnbarry8185]

I have watched hundreds of videos, and NONE of them have explained things as well as you have. Thank you for the explanations and the simple wording. I am sure that you could have made it sound too technical, like so many more channels. PLEASE keep up the good work.

[@Popart-xh2fd]

Nice video. The 2N2222A handles 800mA, meaning that if the restriction depends only on the transistor, the right resistor would be (5 - 0.7)*100/0.8 = 538 (560 ohms). So, the solenoid would be destroyed but not the transistor!

[@curiosity551]

What about the power loss that occurs between base emitter junction due to low resistance? Cant ignore that either.

[@eelmot63]

right what I was going to say

[@AlienRelics]

10, not 100. As a switch, base current should be 1/10th of collector current. Read the datasheet.

[@kissingfrogs]

@@AlienRelics Can't help think that Ben has been scarred by destroying many transistors when he started out that he errs on the side of minimizing base current. 1K would do the trick.

[@AlienRelics]

@@kissingfrogs Perhaps. But beta varies from batch to batch, device to device, temperature, and time. I'd accept 15 or even 20, but 100? That is the rated beta in the active region. You'll destroy more transistors with excess Vce drop at higher current.

[@jojomevo1]

I am sorry for myself lost years in college without understanding pnp / npn ... obviously my instructor was confused himself ! . you made it soo clear and understandable as abc123 .. logic thinking , no extra long talk nor brief short one. just IDEAL explanation. .. many thanks bro ...

[@mikelemon5109]

So what do you guys think about biopolar transistor are they getting too old since the mosfet ones got more efficient and popular or is it just me? for all my applications I use FETs and can hardly think about using biopolar yeah FETs are a little more expensive but still the low 'ON' resistance (Efficiency) is well worth it.

[@hawkcrave]

"A little more expensive" can add up to a lot more expensive if one is building hundreds of thousands or even millions of widgets, with each widget possibly having many transistors. I would guess most companies simply go with the least expensive option that meets the requirements.

[@mikelemon5109]

Yeah but the very high efficiency translates in to a more quality product when it comes to power consumption and simplicity anyway mosfets get cheaper and cheaper over time.

[@hawkcrave]

True. It would then depend on what the requirements were, and if reaching higher efficiency is more important than reducing costs. In some cases it would be worth it, in other cases, not so much. But either way, you've made me think about it and I will do some more learning about BJTs and MOSFETs so I actually have a clue what I'm talking about lol.

[@mikelemon5109]

Yeah that would be great!

[@anullhandle]

Michael bjt transistors aren't inferior because they're older they happened to be discovered 1st. Fets are a cousin to tubes which came before that. Tubes still have their place. darpa is still pouring money into tubes. a plain old 3904 bipolar isn't going on the scrap heap any time soon.

[@kaungmyatkhaing7550]

I am an EE student and this video helps me quite a lot for my project. Thank you for the video!

[@theBang4thebuck]

That was wicked awesome man, thanks a bunch.

[@paparoysworkshop]

Very good explanation. Just the right amount of information for an introductory of how to use a transistor as a switch.

[@greencactus8257]

Hi :) Great video Just one question: why did you say in the beginning that the pnp doesn't have a way to limit its base current? Shouldn't a resistor work as in the case of the npn?

[@avid0g]

Andrei Stefanescu, since the logic input signal varies between 0-5V and the emitter is at +12V, the base current can never reach zero. Thus the PNP device is a poor choice here. On the other hand, if the logic -input- output varied 0-12V it would be acceptable.

[@adon2424]

@andrei, think opposite. in an npn a + voltage at the base turns it on. in a pnp a + voltage at the base turns it OFF. 12-5=7VDC across the emitter/base juction, because you have + 12vdc at the emitter.

[@renakunisaki]

@@avid0g so you would use that if you needed a 12V signal to control a 5V device?

[@avid0g]

@@renakunisaki My point was that an open collector logic device with a resistor pulling up to +12 volt would have the correct output. The logic device needs to be rated to handle the +12V. An NPN would also translate, but with inverted logic. One downside to resistor pull-up is the RC time constant rise waveform.

[@Javii96]

I've been using npn transistors for a few years and Never fully understood why sometimes they work in my circuits and sometimes they don't. So glad I stumbled on this 9 year old video!! thanks

[@beboba2498]

in your circuit you need to add resistor between base and ground e.g. 100KOhm to avoid floating base Good tutorial though

[@AppliedScience]

Beboba This tutorial discusses bipolar transistors, which do not have floating bases, and do not need such a resistor. An insulated-gate transistor such as a MOSFET or IGBT have high impedance gates that may need a resistor to tie the gate high or low.

[@beboba2498]

Applied Science Interference from nearest components can easily turn the bipolar transistor on. E.g. if you have high voltage generator.

[@Akfloatable]

+Applied Science Can you explain what a floating base, or floating anything is? I see this mentioned a lot when reading about electronics.

[@AppliedScience]

+Akfloatable Leaving a pin of an electrical component not connected to anything is considered "floating". This means that the voltage at that pin can change very rapidly if there is nothing to sink or source current. Turn on a digital multimeter to its voltage range, and leave the test leads disconnected. You'll see the voltage floats around. For some components like bipolar junction transistors (BJT), leaving an input floating is not particularly bad because the device requires a fair bit of current to operate, so the pin will remain fairly stready by itself. A MOS component requires almost no current to operate so the slightest bit of charge will cause the pin voltage to change, and turn the MOS on and off very rapidly or partially, which is not good.

[@JasonDoege]

+Beboba BJTs are current activated devices (current from base to emitter establishes the current from the collector to emitter.) If the base is floating, there is nothing to induce a contiuous current from the base to the emitter, an electrostatic charge, while a very high voltage, doesn't have enough charge to induce a large enough current to turn a small signal BJT on. FETs have the issue you discuss where they are voltage activated devices (voltage between the gate and source establishes the current from source to drain) and can easily be turned on by stray voltages. All that said, very high gain BJTs (especially darlingtons) can be briefly turned on by small electrostatic charges.

[@tensor131]

very clear - excellent. This is the first vid about transistor calculations that I actually understood all the way through. So many jump over a detail, especially that bit about the 0.7V drop and I think I'm missing something when actually it as the presenter who missed something. This was so very clear - thank you.

[@irvingkurlinski]

I've got two bread boards. I can make a ham on rye on one of them.

[@willie_mccoy]

I tried that once, but the wires kept getting caught in my teeth.

[@PsyMongazoid]

Wow. That was well explained. A no nonsense, real world, application of components to make a smooth working circuit.

[@jeffrye7846]

What you didn't cover was how you chose your diode and which one.

[@benjaminfacouchere2395]

electronics.stackexchange.com/questions/110574/how-to-choose-a-flyback-diode-for-a-relay

[@harikishorerp6237]

168 dislikes from PNP transistor fans? Such an amazing tutorial explained in the simplest way imaginable!

[@gkdresden]

Thank you for this video. The application of transistors as a switch is explaned very clearly. There are several different semiconductor switching devices you can use for different purposes. A BJT is the simplest device to control. You can switch very high voltages very fast by use of BJT. Its disadvantage is that it is controlled by a current. So if you want to control very high currents, the BJT is not the best choise. It is better to use a MOSFET. Using a MOSFET you only need control power to chance the gate charge. When the switching state stays the same it requires (nearly) no power. The disadvantage of MOSFETs is their lower switching frequency, because the gate acts as a capacitor. Allready at several 100 kHz (re)charging the gate within less than micro seconds requires several hundred mA or even a few A. Another problem of MOSFETs is that they are high current / low voltage devices. High voltage MOSFETs require more gate voltage and have higher channel resistances. A 30 V MOSFET has usually a channel resistance of a few mOhm. A 500 V MOSFET has typically several 100 mOhm or even several Ohm. If you need to switch high currents at high voltages there is another useful device, the IGBT. It combines the low control power of the MOSFET with the high voltage capability of the BJT. A BJT has a saturation voltage for a certain collector voltage. It is typically between a few 10 mV up to a few V for very high currents. So for high voltages and high currents a IGBT is more efficient than MOSFET, whos source-drain-voltage is proportional to the channel resistance. If we consider a 500 V, 20 A (10 kW) switching case and compare a MOSFET with 1 Ohm channel resistance and a IGBT with 1 V saturation voltage. The MOSFET generates a voltage drop of 20V at 20 A and consumes 400 W of power dissipation. The power dissipation of the IBGT is only 1 V at 20 A or 20 W,

[@shoofle]

omigosh i have been an electronics hacker since i was a kid and i think i've never gotten such a solid grounding of how to work with a transistor. i'm 100% going to use this as a reference on my next project

[@acmefixer1]

Very informative, concise video. One important thing about Darlington pairs that most don't know. The two transistors are connected so that the second transistor cannot saturate, it can't fully turn on. There will always be 0.7 volt or more at the collector. This means that the Darlington pair will always dissipate more power than a single transistor. If the Darlington pair is switching 5 volts, there will be more than 10% of the power wasted as heat in the Darlington pair. So it is not a good choice for a switch. Thanks for the great video.

[@ibewatchinu]

Brilliant. Up to now I've bought transistors based on someone else's circuit. Now I can choose my own. Thanks very much.

[@marwansallouta2101]

Very clear and explanatory, thank you. Never late to watch such educational videos even after a decade. It was brilliant.

[@tito51rivera15]

This is what engineering is about .. something complex and making it simple.... thank you

[@adamapsitis6325]

Just wow. I have never been able to grasp the basics around transistors, yet your video seems to have demystified it to the point I could confidentiality use them in a very simple circuit. Thanks soooo much.

[@tnekkc]

I already know every word of this.... and it is on applied science! Usually applied science is a little over my head. I designed switching power supplies for 30 years.

[@DungHoang-dc2qd]

this is seriously the best lecture I’ve had about BJT on the Internet. Keep up the good work Mr.

[@JosephAMuniz]

Damn! THANK YOU SOOOO MUCH FOR GIVING AN AMAZINGLY COMPREHENSIVE TUTORIAL ON TRANSITORS! I had always wondered why the hell transistors never worked when I applied a voltage at the base, and now FINALLY, IT ALL MAKES SO MUCH MORE SENSE! A MILLION THANK YOU'S!!!

[@neilphilip2320]

Really excellent explanation of some basic ideas around transistors! I'll get my son to watch this because he has a fear of electronics and this is pitch perfect. Thx

[@vortextube]

Your video connected much of what I knew to be deficiencies in my electronics knowledge. Couldn’t believe how much is in this one piece.

[@slviopnai6448]

Very good tutorial about designing a circuit by using transistor, put more about this topic very interesting to watch and learn

[@Caffein780]

Thanks man...your ability to explain complex system is awesome. It is fortunate for me that you post these or I'd be lost. Thank you.

[@mtkimbrell]

Glad I ran across your channel. I am an EE working in the field and also work part time as an adjunct professor. You did an outstanding job in simplifying the explanation of a practical situation of component use. I admit that I wish I could make it that simple for my students. I will strive to be better. ;-) Thank you for the challenge.

[@andronatroncoulomb9299]

I've been trying to wrap my head around transistors this whole semester of solid state electronics and motor speed controllers. You are a great teacher, I understand why I let the smoke out now.

[@GMC997]

You are a savior! All the other people on KZbin are explaining it to fast, like it would be self explanatory or sth. Thanks!

[@SmithDrewSmith]

I have to go through this every time I use a transistor because I never bothered to understand why they work like they do. Now I think I understand it well enough I might not have to come back next time. Thanks!

[@ltc0060]

I wish that our teachers in university would explain subjects just like you did in this video; simple and clear, which would increase the quality of education... thanks, great tutorial.

[@ralphacosta4726]

Just what i needed. I have a design concept, but needed some practical info on sizing components. This was perfect. Thank you.

[@ddacombe4752]

Excellent video showing design and thought process, this has been a huge help. I am just building something to control a water stop valve, but the stuff I learned from books and at university never showed how to design a circuit for a real world situation.

[@IrishDublinDave]

I've been reading about transistors for a few days now and this is the first tutorial that actually makes it clear to me, thank you!

[@billysunerson]

I have spent weeks watching KZbin videos and even trying out the Great Courses plus series on electronics. Your video is hands-down the most educational and clearly explained thing on the internet. Thank you!

[@WayneTheSeine]

Very good instructional. I am a little thick and need to watch it several times to get it down but I am on way to total understanding of proper resistor selection. Thanks

[@dolphus333]

As someone who routinely removes protection diodes, I appreciated the detailed explanation of the relay inducance pulse. I may leave a few more diodes in my circuits now :)

[@joshcook7907]

Taught me a lot more than I thought when I clicked on your video. Thank you.