What is a transistor? How does a transistor work? Part 2

[hurrrrrrrrrrr]

You are a good man.

[ram9491685639]

Awesome explanation first time ever I feel transistor

[sonicfuker]

Wow, you are freakin' cool.

[GraysonDean1990]

you are as passionate as my Russian professor, but only 10 times better....:)

[Minnie1799]

BRILLIANT!! THANK U SO MUCH!!!

[drmns]

Great videos. keep it up.

[meholah]

what a fantastic explanation. the parallel between the basic amplifier circuit and a voltage divider gave me a stronger fundamental understanding of the operational range of a transistor. ty!

[123arskas]

You are my Teacher !!!!!!! I Love your Simple Explanations. Albert Einstein also liked to explain things in a simple manner !!!!

[Sekuhara]

First of all - amazing explanation! I truly felt enlightened after watching this.

Previously, my knowledge of electronics never got further than the simple DC circuits with resistors only (Kirchoff's law, etc). Capacitors, inductances and semiconductors always seemed black magic to me. Now that I know that the transistors are used just as a special kind of variable resistors, and capacitors as plugs to prevent direct currents flowing to other segments, I feel much safer in this deadly domain :)

[Sekuhara]

Just one question regarding the transistor inverting the signal: wouldn't it be possible to just put the transistor in the top segment of the voltage divider and a conventional resistor at the bottom? Low input voltage would cause output to align to 0, and the high input - to Vcc?

[SteelWheelsDown]

@Sekuhara, it is certainly possible to do that. In fact, in most circuit outputs, especially for logic and computer chips, there is a transistor in both the top segment AND the bottom segment. These two transistors act as a pair, and complement each other, so that as the lower transistor conducts, the upper one does not, and vice versa. This is why they call them CMOS chips - Complemetary Metal Oxide Semiconductors, a complement pair of MOS transistors making the output stage.

[Phrazemaster]

Wow! I can't imagine a better explanation! Thank-you so much! Just like you said I had been trolling the internet and youtube trying to understand the transistor, but you turned on the lights for me in a HUGE way! You sir, are a brilliant and gifted teacher!! Thank-you!!!

[praveensmile99]

sir ,u r the one who explained about the transistor a lot in a quite short time.

please explain us the mechanism inside it.i mean how a transistor can produce required resistance for respective input signal.can u tell me which book is better for electronic devices and circuits.

once again thank u very much ......sir(awaiting for ur reply)

[GiorgioCapocasa]

Very clear :) I really liked that. Please, keep on posting.

[DarkGuardlan]

You are exactly the kind of teacher I'd like to have, I've had the guy that teaches amplifiers explaining to me how the hell it works for 3 straight hours, and he would NEVER give me straightforward facts like you do.. The problem is, if I can't understand something, I will not spend time learning other theoritical stuff about it, it is pointles..

Thank you for this great vid !!! !!!!!!

[MattTrevett]

Thanks for the help here. In your simple amplifier setup could you not use the transistor a little differently to avoid the phase inversion? IE, using the transistor emitter as the V out, and wouldn't that eliminate a few resistors? There might be downsides to that if it even works..

Once again thanks for your help, great videos.

[svallam]

Awsome. you are a very good teacher.

[bvzeggy1]

I love you man

[Paggee]

Great video! Is there a part 3? Cant find it :(

[ransom1wi]

OMG you have got to be kidding me, I've been up for 36 hours trying to figure out transistors and all the crazy equations that come with them, I've even went as far as to building a few examples in my head to try to help "visualize" the Q point and the voltage trails and now some crazy man on you tube is saying the way i learned it is wrong and that's why it makes little to no sense.

[ransom1wi]

Well Sir. I'm a little bit senile at this point but If you are a teacher please tell me where you teach because I will transfer in a heart beat. I want to learn!!!!!

[marcin1337]

Thanks for this video, I just recently made a flyback driver using a Nchannel Mosfet and 2 PNP and NPN bi Polar transistor, your video helped me understand how the AC was made.

Sadly I don't have a flyback yet, I had a test transformer but I blew it up :D

Do you know if the hz of the AC effects the performance of the transformer?

[chancerogers85]

@SteelWheelsDown So basically a transistor is kind of like a varying NOT gate? if the input is low then the output is high.

[SteelWheelsDown]

A transistor (bipolar junction) is a variable resistor whose collector-emitter resistance value goes down as the base signal goes up. In a voltage divider where the transistor is on the bottom, yes, the output of the divider will be inverted, and it can only sink current. If the transistor is on the top, the divider output is just a buffer, and it can only source current. To both source and sink, the divider can have transistors in both top and bottom (TTL, or complemetary push-pull setup).

[JosephPatrickMcmahon]

F'ken genius. This is the first time in my life that I have understood this fundamental concept of one of the great inventions and enablers of our time. Thanks Joe

[homosapien160]

sir please give a separate lecture on Vcc and Vin.....these two cause confusion!!!! i khoW the difference b/w them but wanna know detail so that i might become very clear abt everything.....THANX

[mbsfaridi]

So how do microprocessors calculate and do other stuff by just transistors resistance changing?

[SteelWheelsDown]

@mbsfaridi, transistors are at the heart of microprocessors. Transistors are used to construct logic gates (AND, NAND, OR, NOR, NOT, etc.), and logic gates are put together to create larger circuits like flip-flops (bi-stable multivibrators, capable of "storing" a value until its input changes). If you give each "bit" its own flip-flop, you can string 32 of them together and get a CPU register. Digital counters, shift registers, binary adders - put all of that into a chip, and that's a CPU!

[mbsfaridi]

@SteelWheelsDown

Oh okay but how does the ALU calculate?

[mbsfaridi]

@SteelWheelsDown

Basically i mean how does the cpu understands and put it up on screen.I googled it and various other thing on how a computer,transistor or a microprocessor work but couldn't find anything i could understand but my transistor problem,which on solved thanks to your videos.

[zikrizainal]

i still don't understand at 6:12, you showed us graphically on how the output voltage (Vout) changes according to the input voltage (Vin). i do not understand why an increase of Vin at the base causes a resistance drop in the transistor? and what is Vin compared to the original Vcc? are you saying there are two different potential difference. please kindly explain anyone. thanks. your video is really changing my perspective about the transistor.

[THETRUTHOWHY]

love you dude so funny

[thequnson]

thanks again

[Aerospaceman]

My training in electronics included vocational and military schooling and no where was it explained in this manner. The transistor is a bridge between two words: transforming + Resistor = transistor. Spending all my time trying to understand collector, emitter, and base then applying saturation cutoff and biasing, this is so much easier to understand. Thank you

[TheMegalucian]

does ground mean negative?and V in mean pozitive?

[suleman263]

Excellent tutorial .



[myworldismine72]

Hello i really like your video

You explain verry well

Can you make one video for the 555 timer

cause all the tutorial on the internet not explain well like you

[TheGurujeee]

@SteelWheelDown I have a question. If transistor really is just a variable resistor then its resistance should be constant for a given voltage (Vbe) rite!? Now lets assume a series resistor, transistor circuit, if the resistance of the collector is changed and Vbe is kept constant then total current value across the circuit should change. But we know from theory that current only depends upon Vbe value in active mode regardless of series resistor. can u please clarify

[darthvader906]

this was very helpful. still a little confused on how the biasing works

[LiKBeAsT]

I rarely leave comments, but... congratz! :) Very nice and helpful. Really enjoyed it!

[dasraiser]

i feel i need to face palm, a voltage divider, so simple. thank you for posting this :D

[smartestguy999]

Thanks, helped me to understand how to use transistors as NOT gates'

[DarkLevis]

This is excellent, took me a while to fully understand though as I'm not ań electronics student but your explanation is great. Would be great to get some values of the 'transistor voltage divider'.

[bazengao]

i have a battery that it's out put is 10.8V at 4 amps and i need it to be 9V and 3 or 2 amps, my dad told me to use resistors and i don't know how to use them. could you help me out pls?

[hi2myhomies]

where's the third part? aniway great job mann.. it was a really helpful informaton...

[sectasyotuberas]

Un transistor es un dispositivo electrónico.

[veryfuck]

can you please help me? on wikipedia (dutch) they say a transistor uses a current and a FET uses voltage. i dont understand thats, basicly they are saying there flows a current from the base to the emiter. thats what i dont understand because i thought that was not possible and the base is only used to set a signal (voltage).

im really confused now because after your video i though i understood and now wikipedia is lieing to me.

[hhhvelocity]

It was awesome. . . I have many doubts. . . Pls give me ur email id. . .

[manvscode]

Great video. Maybe the best transistor tutorial on youtube. Afrotech's is pretty good.

[TheOriginalMack]

thank you

[youspinmerightrounds]

Great video! It's always difficult to find worthwhile tutorials!! I've a pretty basic video made on my channel which may help people too.

[rulyvideo]

Im ready to create my own iphone, lol, very nice xplaination indeed!

[tangnatalaga]

@rulyvideo you need millions of those transistor to make an iphone. lol . You can make a simple mic amp with a single transistor though. Then you can sing karaoke with your stereo receiver. Since the RCA jack to a reciever will not amplify signal from a microphone. You can put the mic on the left input and the music on the right and you have a one transistor karoke machine connected to youtube. lol I made one for my friends one time. We had a good time.

[abhishekjetely]

I wish if U were my teacher, :)... thanks for uncomplicating my mind, it was really very helpful ... sorry for my bad english!! :)

[bergerlemur]

Your educational videos are great. Are you a teacher? If not you've got a natural talent.

If you had videos for all basic EE concepts at least, I could basically not attend class.

[Nadrealis]

I have a question even though I fully understand how a transistor works. Why is the output of the transistor on the collector side even though the npn transistor clearly shows current running towards ground. Is it because the schematics are flawed since electrons actually run from - to + instead of the way they teach us?

[SteelWheelsDown]

@Nadrealis - The current output of the transistor and the voltage output of the circuit are two different things. I used conventional current (flows pos. to neg.), and current flows across the transistor toward the emitter. Regardless of which way we say the current is flowing, the voltages will remain the same. If you use electron flow, the current input is the emitter (electrons are emitted there) and the output is the collector (electrons are collected there), why they are named that.

[Nadrealis]

@SteelWheelsDown I built the circuit you showed in Multisim and after playing around with resistor values and capacitor values.. I have no idea what I built, I essentially turned a 10V 120 Hz sine wave into a blocky one at the 2nd transistor's output..if you'd like to see what I mean let me know. I have no idea what I did so it's obvious that I'm confused lol

[tangnatalaga]

Respond to this video... So this cicuit is actually also an inverter. Since the input signal is opposite of output voltage.

[tangnatalaga]

Respond to this video.. When the transistor is fully on ( saturated ) and conducting current the voltage drop across is almost zero. You are actually measuring voltage drop at the collector. Since you are measuring it in respect to ground potential. Which is probably how you would use the transistor. If you have a resistive load from the collector to ground and since resistors are voltage dependent, the resulting current to the resistive load depends on how much the transistor turns on.

[xobinary]

Wow, after that impressive explanation I just had to sign-in and comment on the beautiful simplicity of your video. I love electronics and even planned on becoming EE, but after 2 years of University classes that constantly dwelled on everything EXCEPT what you covered in your video, I decided to get my degrees in Mathematics and Computer Engineering. I was too afraid my EE career would be acting as a chemist of physicist calculating beta values and hole configurations instead of designing :P

[hondaazuzu]

Thank you. It's worth noting that my electronics prof yells in the exact same voice. must be a nerd thing. Can't beat a free education though.

[sloppyoscar]

Actually, I meant that if the current goes up (assuming I'm correct) then the resistance or impedance must go down, right? I'm sorta new to all of this. Thanks

[SteelWheelsDown]

@S.O.: This is a voltage amp, so whatever is hooked up to the circuit's output should be pretty high-impedance. This is because whatever is hooked up to the amp's output is in parallel with the transistor, so if the output's resistance is low, the transistor's change in resistance won't have very much effect on the overall resistance in series with R1 - having the transistor go into cutoff (infinity) will be nullified by the resistance of the output device. This is not good for an 8-ohm speaker

[sloppyoscar]

@SteelWheelsDown Ok. By parallel you mean that after the current running from the voltage source goes thru R1 it can then either continue going down to the transistor (a resistance source) or thru to the Vout and what load it connects to. This makes the hooked up device and the transistor in parallel.Correct? I then understand that an 8 ohm device, being low impedance, could easily be done in by high voltage. Thanks, I promise not to turn into a full-time student. Oscar

[tangnatalaga]

@SteelWheelsDown I agree with you because the transistor is biased so that it is mostly turned off, but I don't know why there is no capacitor at the output since class A amplifier is for audio. You don't want all the DC on the speaker anyways.

[SteelWheelsDown]

@tangnatalaga My bad - I put one on the input and not the output, and you really need both for one of these circuits. A push-pull power amp can amplify without the DC component at the output though.

[tangnatalaga]

@SteelWheelsDown It is okay since a class A is not usually used as the output of an audio amplifier. Rather it used to drive another stage where a coupling capacitor is not used.

[SuitS06]

@sloppyoscar yes that is correct, they are inversely proportional to one another. Therefore, if the current increases the resistance (DC) or impedance (AC) must have decreased to allow for more current to flow through.

[tangnatalaga]

@sloppyoscar You have to start with a supply voltage with a given ampere such as 12volts 600mA etc. Lets say you put a 1k ohms (1000 ohms) resistor in series with that supply to the ground. You would divide 12 by 1000. Which is 12mA of current. At this point the voltage remains the same but the current across the resistor is now 12 thousandth of an amp at 12volts. This is ideal for powering a single LED for example since most LED can only take a maximum current of about 20 mA or so....

[tangnatalaga]

@sloppyoscar Always think of resistors as a device for lowering current not increase it. Thats why it is called a resistor. Some device need certain amount of current to function properly. So you use the right value resistor. If you exceed the maximum operating current of a device it will fail. For example if you have a transistor that has maximum operating current of 1 amp it will fail if you exceed that. A good circuit design uses only half of the maximum operating current for reliability.

[tangnatalaga]

Respond to this video... Here is another thing. Lets say for a given resistor in a circuit, If you increase the supply voltage, the current across that resistor will increase as well. Now if the voltage is unchanged, increasing the supply current will not increase the current across the resistor since a resistor is voltage dependent component. That means even if you use a car battery capable of cranking a car it wont burn out an LED as long as you have the 1k resistor in series.

[tangnatalaga]

Respond to this video... I think I should put up on how to make a youtube karaoke machine for less than five bucks using only one transistor two resistors and two capacitors. As long as you have a reciever with a RCA jack input. I made one for a party one time and it uses two AA batteries. You can buy a cheap dynamic mirophone at the 99 cents store. lol It sound pretty good actually. 

[sloppyoscar]

Wow. I really enjoyed this! This circuit is much clearer now. However, I do have a question -- you mention that the output voltage cannot go above the supply voltage so does that mean that the purpose of such an amplifier is to increase current? If so, then I guess that means the resistance or impedance of the output must go up as well . Correct?

[SteelWheelsDown]

@S.O.: The common-emitter circuit is a voltage amp. The current output of this is limited by the collector-side resistor, R1. This is why it's referred to as a current-limiting resistor, so the maximum current this thing can "source" is supply voltage divided by R1. On the other hand, the transistor's resistance when saturated is zero ohms, so if there's some voltage from the output hookup, this thing can "sink" enough current to destroy the transistor if you're not careful.

[maktry]

good job ... برافوووووووووووو

[mgewell]

This is awesome! First time I've understood a transistor! KC5IZN

[elhuchepo]

Wow! It's about time someone explained electronics in plain simple English, keeping us in-tune with humor! Thanks alot and please keep adding more videos!

[Mnmonical]

Dude, you're video's are the best! I don't know why it's so hard to find anyone who will explain how electronics work. Thank you so much!

[ChaseKolpath]

Holy cow.  Awesome, awesome, awesome explanation.

[1avlonj]

This is by far the best video/documents explaining transistors!!! Would love to watch more videos from this author!!! Thank you very much for taking the time to make this vdeo and sharing all that knowledge in a basic manner!!! Right after viewing this I made my own circuit turning a LED on. I also now know what Sinking(NPN) means!!! You the MAN!!!

[SteelWheelsDown]

@1avlonj - I'm like Tony Stark's dad. I've had this story in my head for over 20 years, planning it out, adding to it, refining it, but until now, I haven't had the technology or the time or opportunity to share it with anyone. Thanks for watching.