Why NPN transistors are more often used in circuits?

In this video, we will find out some of differences between NPN and PNP type transistors and why NPN transistors more often seen in circuits and other important things about transistors. Please stay with me in the rest of this video.
BJT transistors fall into two major categories, NPN type and PNP type. But the main question is “Why NPN transistors are most popular?” or “Why NPN transistors more often seen in circuits?” or “Where should I use NPN and where should I use PNP?” these are very important and confusing questions.
Before answering these questions, we need to know what are transistors used for in circuits! This is good question to start with. Transistors have two main uses in electronic circuits.
No1: Transistors are used for amplifying voltage or current, mostly in analog circuits.
No2: Transistors are used for switching voltage or current, mostly in digital circuits.
Since digital circuits like microcontroller based circuits are more popular these days, we often see the second usage of transistors, I mean using transistors as a switch.
For a switch to work properly, it must be placed between the load and the power supply. No matter the switch is placed in positive side or negative side of the power supply. But if you need to use a transistor as a switch, it is important to place it in correct side.
Where to place the transistor? on positive side or on negative side? This is a question that rises from this content!
which side of power supply is better to place a transistor? Answer of this question is depends on transistor type you are going to use. If your transistor is a PNP type then you have to place it on positive side of the power supply and if your transistor is an NPN type, you have to switch negative or ground side of the load.
With a little study about BJT transistors, you can learn about them and about their 4 operation modes; saturation, forward active, cut off and reverse active modes. When the transistor is to be used as a switch in digital circuits, it must be only in two modes of operation, the cut-off mode which the transistor act like open circuit when switch is off or forward active mode which the transistor acts like short circuit when switch is on. Transition between these two modes is very easy and straight forward in an NPN transistor, because of that, NPN transistors are handier and useful and more seen in nowadays circuits.
You may wonder why switching of an NPN transistor is easier than its PNP twin! Let’s discuss about it.
According to our basic knowledge about BJT transistors, base-emitter voltage in NPN type and emitter-base in PNP type should be more than 0.7volts to turn the transistor on and take it into forward active mode otherwise the transistor will fall into cut-off mode and will turned off. In addition the emitter pin must be connected to power supply and collector pin is always connected to load in both types, NPN or PNP. Other fact that we know about BJT transistors is that NPN is for switching ground and PNP is for switching power supply voltage.
Let’s suppose that the load is a 12 volts DC motor. Because of that, we need a 12volt power supply. Emitter pin of NPN transistor must be connected to ground or zero volt, and emitter of PNP type should be connect to 12 volts.
With these assumptions, if you try to switch the motor using NPN transistor, you simply need 0 and a voltage over than 0.7 volts which is available on every IO pin on any microcontroller. But if you try to switch the motor using PNP transistor, I have bad news for you, because the transistor will turn on with 11.3 volts or less and turn off with base voltage higher than 11.3 volts. You can’t turn the transistor off using microcontroller and of course you can’t stop the DC motor, because MCU pins can provide 0 and 3.3 volts or sometimes 5 volts which all of them are less than 11.3 volts and all of these voltages turn the transistor on. This is main reason that NPN transistors are used more than PNP types.

[@ke9tv]

For various technical reasons, it's easier to make an NPN transistor switch faster and consume less power. The underlying reason is that the charge carriers in NPN devices are electrons, while in PNP devices they're holes. Electrons have a higher mobility than holes. Because it's harder to get the same performance in a PNP as in an NPN, PNP transistors are used mostly in class B amplifiers, in H bridges, and in sensing circuits for which a short to ground must be detected as a fault. Even in these applications, a Sziklai pair is often preferred, with the high power being switched by an NPN transistor with a PNP controlling its base. Back in the day, PNP's were commoner, because that's what could be made in germanium point-contact transistors. But ever since the advent of silicon, N-channel FETs and NPN transistors have been cheaper, faster, lower-power, and capable of handling more current than comparably-priced complementary devices. (Excluding anomalies like PMOS memories, which flourished during a brief interval when a process for making NMOS or CMOS ones was not completely developed.) In fact, it's arguable that your observation that microcomputer outputs are basically current sinks and it's easier to pull the transistor base to the negative rail - driving the popularity of NPN devices, puts the cart before the horse. The microprocessors work that way precisely because the transistors do.

[@elewizard]

Thank you for sharing these valuable information 👍

[@jonlitchfield8888]

Thx so much for taking the time to post that, i found it clear, really informative and well explained

[@dr_jaymz]

I think this is the right answer. I was told that back in the day it was always a much bigger challenge to make pnp transistors that matched their complementary npn counterparts. They were larger, a bit more fragile and often wouldn't quite be a match for npn. I think nowadays this is less the case but npn is already king. Then simplicity comes into it, its just easier to arrange a low side switch, if you used pnp you'll need a npn to switch it because the high side voltage will usually be beyond the device voltage you're driving it from, whereas for low side they can share the same ground even though the collector can go to full supply.

[@Spark-Hole]

Nowhere in any transister data sheets say that NPN is faster. You must be an insider. Thanks for knowledge.

[@tedbastwock3810]

cart not card ... but thank you, that's very informative

[@MlokKarel]

I owe you a few beers, man. With your help I eventually might learn what I wasn't able to when I was young (even though always being attracted to electronics & computers...) 🍻

[@elewizard]

Thank you dude, I am so glad to hear that. 🍻🍻🍻🍻

[@jacksparro3150]

You can use a small NPN transistor with its collector connected to the base of the PNP transistor and a resistor connected between the base of the PNP transistor to the supply voltage. An additional transistor allows microcontrollers to switch NPN transistors that if you find yourself needing to switch the Vcc line instead of the ground line.

[@elewizard]

That is right 👍

[@yankozlatanov]

Exactly what i was going to write. This is little more expensive and complicated, but if you really need to use the pnp with microcontroller is your only option for higher voltages than the microcontroller uses.

[@westsidepimping]

Good tip! Thanks

[@wilbertzgroup3561]

Where were you all this time. I have never understood transistors better than what l have learned in this short video 🎉 More videos please 🙏

[@elewizard]

Awesome, new videos are coming soon 😉

[@SuburbanDon]

I should have figured this out but I did not. Thanks.

[@kothapallysandeep587]

Good explanation.keep posting on cricuit analysis

[@elewizard]

Thank you, I will

[@pault6533]

Thanks for answering questions I always wonder about but forget to investigate. "You may ask yourself" reminds me of the Talking Heads song Once In A Lifetime.

[@RixtronixLAB]

Creative video, thanks :)

[@elewizard]

Glad you liked it!

[@vasily_chivanton]

I'm looking at old germanium transistor circuits. And they're almost all pnp. Why didn't they think of using npn then, since it's so much easier?

[@elewizard]

In old circuits the logic was opposite of the logic nowadays. I mean in that days, positive voltage (VCC) was used as common voltage. So, in those days, using PNP was much easier and more common 👍

[@ServiceOrchestramegastore]

well, electronics is not so complicated when its explained neatly!! Thank you..

[@elewizard]

Glad you think so!

[@ksdls2002]

Thank you. I need a similar video for mosfets N and P channels. Please.

[@elewizard]

Noted👍

[@keskinli3446]

Hap gibi bilgiler . Teşekkürler.. Türkçe yazdım çünkü bu kanala denk gelen kardeşlerimiz takipte kalsın çok pratik ve pek değinilmeyen konulara değiniyor bu usta...

[@elewizard]

Teşekurler 🇹🇷

[@jurijavsenak]

Thanx. Very clear description. You have a new subscriber. 😊

[@elewizard]

Welcome to my channel 😊

[@tnamen1307]

​@@elewizard​can you explain this??? Why the input switch is always kept at the base side?? Can not it be keep at the power side of the collector with base and emitter keeping constant??? Or, can not it be kept at the emitter side with base and collector side constant??? Please explain.

[@salih869]

I need to trigger an ecu with arduino with a 12v positive load. I don't have enough space to use a 4 channel relay. Can I trigger Tip217 transistor with BC547? The ecu will not draw much current, but since I am not sure, I am thinking of choosing Tip217. I plan to line up type 217s side by side, give 12v to their middle pins (collector) and get the output from the emitter according to the Arduino trigger. Can this system work stably for a long time? Should I give 12v or 5v to bc547 to trigger type 217?

[@amir2010r]

خیلی خوب توضیح میدین وب سایت هم دارین؟

[@elewizard]

Thank you amir. No I haven't website yet

[@tnamen1307]

Please explain... ​can you explain this??? Why the input switch is always kept at the base side?? Can not it be keep at the power side of the collector with base and emitter keeping constant??? Or, can not it be kept at the emitter side with base and collector side constant??? Please explain.

[@Yorumcu63]

Great video thank you I am member too

[@elewizard]

Welcome aboard!

[@CurmeTheobald-b8f]

Lewis Angela Jones Maria Young Christopher

[@SumaParveen-s4i]

Jackson Betty Jones Edward Martin Thomas

[@absolute___zero]

4:03 what is going to happen if I connect in the opposite mode? collector to power supply and emitter to load? It should work because current flows along the wires of the entire circuit anyway, right?

[@suhailasaba1051]

Thank you for your great video.

[@elewizard]

Thank you for watching the video and being a part of the community ❤️

[@lamtrungrau5986]

very easy lesson, thank you so much Sir. From Việt Nam with love

[@elewizard]

You are most welcome ❤️❤️

[@NoelDuroe]

Williams Matthew Allen Edward Miller David

[@lukechriswalker]

Thank you so much, this knowledge didn't want to go into my brain at school but you made me actually understand how to use transistors ❤

[@elewizard]

Wow, thank you ❤️ your comment put a big smile on my face ☺

[@AmmarAlsadaka]

thanks from sweden

[@elewizard]

Thank you for watching my Swedes friend ❤️

[@rajanne2947]

Nice explanation!

[@elewizard]

Glad you think so!

[@electrotsmishar]

Great explanation.

[@elewizard]

Glad you think so!👍

[@tonylilileija6492]

Hey sir thanks

[@elewizard]

So nice of you

[@mstfztmz]

✔️

[@Savan_Triveda]

From all the electronic channels I saw on youtube this one is the best. I saw many. Thank you for explaining BJ-transistor.

[@elewizard]

Thank you for watching me 😊

[@BStott]

NPN on positive side of circuit as switch. Not ground. Also, don't ever switch ground/negative. You leave circuit energized to power voltage. One 'screw' up and you fry your circuit by grounding. When you switch power side of circuit, the circuit can be worked on and not shorted. Of course, you wear grounding strap.

[@elewizard]

NPN is used to switch ground for a part or portion of the circuit, not the whole circuit. For example, we use an NPN to switch ground side of a relay, a DC motor, etc.

[@rogercarlsson8679]

You probably can't use the NPN transistor directly to turn the motor on/off anyway due to power consumption from the base so I think you need two transistors anyway. That is way a MOSFET is preferable as you described in another video 🙂.

[@elewizard]

Darlington pair transistors like tip122 are available for such applications with hfe about 1000. We can use Mosfet or darlington pair transistors 😉

[@megastar930]

Wow, thank you a lot ❤❤

[@elewizard]

You're welcome 😊

[@samuelromero1763]

Thank you for helping me understand transistors better than my instructor ever could.

[@elewizard]

Happy to hear that 😃 Keep watching, there are more useful content like this 👍

[@brianwood5220]

Highly informative, Thanks

[@elewizard]

You're welcome

[@b1zarre23]

Very good explanation, thank you! Please continue producing videos that break down the components to the most useful information a hobbyist could need!

[@elewizard]

Thanks, will do!

[@sayedhassanphysics8491]

🌺🌹 you are a great 👍 🌺🌹🌹🌺

[@elewizard]

Thank you! 😃

[@smilingdog2219]

Thank you for explaining the basic application and correct side of currants. I'm trying to wrap my mind around a broader relationship of components so I can design my own guitar pedal.

[@elewizard]

Glad it was helpful!

[@jbflores01]

Excellent tutorial! As always!

[@elewizard]

Thank you! Cheers!

[@TheRealEtaoinShrdlu]

You could use a transistor as a clipper on your microphone to remove the popping sounds...

[@elewizard]

Yes, the microphones quality was really low 😅

[@DeenBot20x]

Thanks for the excellent video and presentation

[@elewizard]

Glad it was helpful!🫡

[@Cynthia_Cantrell]

Another side-effect of using a PNP which may be annoying for some applications: When you first turn a circuit board from OFF to ON, the driver for the PNP base is likely to be at ground when you first power-up. Thus, as the power supply voltage rises, this can turn ON the PNP for a short time until the base driver gets up to its final voltage. This means the transistor is ON for a short period during turn-on. This can cause a "popping" sound if this is an enable for an audio circuit, or could cause a glitch in an important signal - say a microprocessor reset line if if is used there.

[@andreoharding5820]

Very nice video ❤

[@elewizard]

Thanks 🤗

[@davem3953]

click like

[@daudisadi6722]

my name is David from in Cleveland Ohio

[@elewizard]

You are very welcome my friend ❤️❤️❤️

[@earthlingthings]

Good info bro

[@elewizard]

Glad you liked it

[@HOLLYWOODlosANGELES]

*Merci pour ces rappels.*

[@elewizard]

Thank you so much ❤️❤️❤️

[@msg1956]

Excellent..!

[@elewizard]

Many thanks!🥳

[@nonsuch]

A question of "why" still remains. Why does the NPN only require 0v - 0.7v for its operation and why does the PNP require 11.3v - 12v for its operation? All I know so far from the video is that those are the requirements for the motor to turn on and off.

[@elewizard]

Also a PNP requires 0.7v but in reverse polarity. I mean they need 0.7v lower than the Vcc, say 12v. So they trigger on 11.3v which is 0.7v away from 12v 🤪

[@amidolamaei5908]

سلطان

[@elewizard]

Joone dadash

[@tedbastwock3810]

Around 4:19 [paraphrase] whether pnp or npn, emitter connected to power supply and collector connected to load ...... this is such a practical, clear, and useful point made for beginners .... if only all teacher could be so clear..... thank you, best luck on your excellent growing channel.

[@elewizard]

Glad the video was helpful. 😃

[@rongray8934]

Anyone else having Blues Clues flash backs? Any way Great video. They are really helpful.

[@elewizard]

Glad it was helpful

[@amilaanuradha8409]

what is your name and country

[@benahmad5867]

Thanks my dear !

[@elewizard]

You are welcome!

[@donaldfilbert4832]

Your video content is excellently and clearly articulated. It is a pleasure to watch them even if I already know the subject - because it is educational to watch how you develop your ideas and succinctly yet comprehensively cover the topics. Thanks for all of your efforts.

[@elewizard]

Glad you think so. Yeah I am spending lots of time on arranging things contents in my videos

[@udance4ever]

so if we only had NPN transistors in this world - would it be sufficient? are there applications where PNP transistors are required & cannot be substituted?

[@elewizard]

Yes, in most cases NPN transistors can be used instead of PNP transistors with a little change in the circuit. But, this may cause non-optimality in the circuit.

[@udance4ever]

@@elewizard good to know it's interchangeable! where can I read (or watch!) more about how the choice impacts optimization?

[@elewizard]

I have no idea. I will make a video on this subject if I have time ⌚

[@3D_Printing]

I heard NPN transistors are easier for manufacturers to make

[@elewizard]

I don't think so!

[@RexxSchneider]

@@elewizardThey were at a crucial time when silicon was replacing germanium. Silicon transistors could be made cheaply and mass-produced by diffusion techniques, rather than the alloy techniques used for germanium transistors. It happened that it was possible to diffuse simultaneously both the base and emitter regions into a substrate which became the collector. This worked because acceptors (which form p-type) of low atomic weight diffuse more rapidly than donors (which form n-type), so that a p-type base could be formed further into the material than the n-type emitter. See en.wikipedia.org/wiki/Diffused_junction_transistor#Double_diffusion for more detail.

[@amir2010r]

please introduce yourself where are you from (i mean which city) and what is your name if it's possible

[@elewizard]

I am your compatriot Ardabil 😉

[@amir2010r]

@@elewizard یاشاسین اردبیل همه ویدیوهاتونو دانلود کردم منتظرم بعدی هستم 👌

[@elewizard]

@@amir2010r thank you so much. Next video is comming in two days

[@y_x2]

The NPN was cheaper to manufacture than PNP also.

[@elewizard]

Is it because mass production?

[@y_x2]

@@elewizard The NPN has two time less resistance than the PNP and therefore smaller and cheaper to produce.

[@RexxSchneider]

@@y_x2 The resistance is merely a function of the degree of doping in a semiconductor. However, electrons are more mobile than holes and that tends to give NPN (which use electrons as carriers) advantages in characteristics (like β and Ft) over PNP. In early silicon transistors, it was easy and cheap to make a NPN structure by double diffusion, while a similar PNP would usually require a two-stage diffusion process.

[@bzfarbodjz]

agha shoma torki ehyanan ? ;)

[@elewizard]

Yes, I am 😉

[@RexxSchneider]

4:26 You state "NPN is for switching ground". That's a mistake. NPN is for switching relative to the positive rail. PNP is for switching relative to the negative rail. You've made the mistaken assumption that ground is always the negative rail, but that's merely a convention brought about because NPN transistors became more common when silicon took over from germanium. You can ground either rail and the circuit works the same. I'm old enough to remember when germanium transistors like OC71 were the commonest, and they were PNP because that was the easiest type to fabricate from Ge. In those days, the positive rail was ground. My first car was positive ground (i.e. the chassis was connected to battery positive) because the radio had germanium transistors. When silicon transistors became more freely available, the easiest type to fabricate was NPN, so we grounded the negative rail. When I upgraded my car's radio to one that used Si transistors, I had to swap the earthing so that the chassis was connected to battery negative, which involved re-magnetising the dynamo's permanent magnet in the opposite direction. So, you actually have it the wrong way around. Because silicon NPN transistors were easier to fabricate (and had better characteristics), they became more freely and cheaply available and hence were used more often in circuits. The negative ground was a _consequence_ of that. And I've got some bad news for you. If you ground the positive rail, then your MCU will run from a -3.3V or -5V supply. It will provide 0V to turn off a PNP transistor or more than the -0.7V required to turn it on. You won't be able directly to turn off an NPN transistor switching from the negative rail.

[@elewizard]

Thank you for these facts. You are completely right, but I think you had better mention these points in IEEE, not KZbin. Here is a place for newbies and enthusiasts, not professionals. I have to present information in a simple way so most of my audience can understand. Talking about positive ground does nothing but create confusion for my audience.

[@RexxSchneider]

@@elewizard You should never underestimate your audience. I do agree though that in your presentations, it is fine to aim for a particular level and not complicate beyond that. However, the comments section is where you can engage with a much broader audience and discuss in greater detail. That allows an opportunity for everyone to learn something new. Thank you for your engagement in the comments -- not every content creator does so well.

[@MlokKarel]

​@@elewizardExactly! I am happy as a clam that I finally understood the practical differences / use cases for NPN & PNP BJTs in circuits, especially in conjunction with MCUs... I finished a med school 15yrs ago, I have neither time, willpower nor strength to do a MIT masters degree in my 40s... 🙄 So thanks @elewizard once again for doing these vids, they helped me to go a long way in those few last months😀👍

[@saint_and_holy_unicorn]

Super explanation!! 👍👍👍👍

[@elewizard]

Glad you think so!