SparkFun According to Pete # 36: Transistor Biasing Configurations

In this month's edition, Pete discusses two of the three major Transistor Biasing configurations, specifically common base and emitter follower.
According to Pete is a video segment starring SparkFun Director of
Engineering Pete Dokter. In this video series, Pete addresses common
engineering questions, discusses current projects, and explores the
wide world of embedded electronics!
Tags: ATP
Talent: Pete Dokter

[@m.edwardburton6247]

Thanks Pete! I'm working on stereo receivers and am having trouble setting the bias on one channel so I needed to learn more about what the heck is going on here in a very specific fashion. Your explanations and editing are great. (Editing can be a problem with some of these other folks videos). You're doing great, keep up the good work and THANKS!

[@user-tg6pb9wt3f]

Hi Pete! I always enjoy your tutorials. I wanted to refresh on transistor theory.. and you are my go to guy! Thanks!

[@rogeryoung7405]

I liked your intuitive explanation of how both circuits work.

[@mikeburch2998]

I thought that was nicely presented and easy to listen to and to learn from. You're a good teacher and not all full of yourself. Greetings from Arizona.

[@JayP7.62]

Thank you! You explain this better than my professor. I find it hard to take notes and at the same time keep up with what he’s explaining. If I’m not taking notes and just pay attention I understand it easier. But then I don’t have any notes lol. So I’ve been taking notes and looking everything up here on KZbin to understand it. I have found a few really good KZbin channels including yours. Thanks again!

[@dr-mnizam]

Here is bjt analysis kzbin.info/www/bejne/iKLTmq1slJiCi9k

[@bhaskarjyotisarma8919]

I luv the way u try to make us understand how to go deep inside of it...

[@CopyCatDee]

You're so COOL! I love the way you speak!! :D Learning from you is fun!

[@mjirvin010]

Finally, a channel that is a) Good audio quality, b) actual english, c) and real-world applicable. If you want to pass a test, go read your circuits i.e. algebra book. If you are a professional engineer that needs a refesher for a quick understanding to get a job done...boom.

[@pedlerw]

On the common base example you mentioned antenna impedance matching as a potential application. Would I be matching "Rin" to the impedance of the antenna? Furthermore, is there a quick and dirty way to determine the impedance of an antenna?

[@therickaman1]

How did you calculate the parallel output impedance at 19:51? I followed the calculations to that point, even for calculating values for R1 and R2.

[@pitito98]

Great explanation. I wish to have seen this sooner.

[@rutgerv]

Damn..that's some great teaching skill! Thanks so much for doing this, learned a lot!

[@mikeburch2998]

He does do a great job of it. It's like having a buddy explain it to me.

[@jlewis184]

a good example of a practical and common use for the common collector configuration is the linear regulator! this is a very useful and interesting application of the emitter follower topology and shouldn't be overlooked :p

[@gfodale]

At about 9:23, you list Vt as 26mV. I cannot find on the data sheet how you came up with that value. If anyone can explain, I would appreciate it.

[@refaymohamed2960]

Thank you, engineer, can we use it in the transmitter circuit for the sake of oscillation?

[@rusty_junk]

Thanks man! Really helped. That input impedance you spoke of in the common base is r π (r-pi) I believe.

[@L1Christopher]

Thank you for your awesome videos.

[@sameermfaroor9856]

You explaination is very catchy and tremendous.

[@MsMadLemon]

I appreciate this, the friendliness of this lesson helps me... and you said sister!! yaay, thank you brother! haha :o))

[@equalsql7508]

I love your teaching style 👍

[@swalker157]

Did you do the common emitter video? Can you post a link to it?

[@zaidyousaf8473]

Sir please explain the concept of stiff and not stiff voltage divider bais? Describe how dc input resistance at the transistor base affects the bias?

[@jeromekerngarcia]

Nice job Pete! Enjoyableand informative, any plans to talk about the Cascode configuration?

[@melmanuel603]

Could you please describe input and output impedance of this circuit and calculations

[@rudodzvore4011]

guys can someone tell me the functions of the three terminals of a transistor according to npn and pnp im having a prob with that

[@321reh]

Very Good Explanation!!!!!

[@shubhamide]

why bjt can not block the reverse voltage?

[@psubond]

You have more patience than i do. I would have chucked that marker across the room when you were writing 5ma

[@avicohen3035]

Can you bias the base of a bpjt , without using a voltage divider. Putting instead, a very high resistance, single resistor? Is there a threshold of current, which below, the transistor wouldn't mind the voltage? Assuming a crude slow switching of a DC. Very soft switching. ? I mean, without the R2. I don't like the R2, because it represents for me, a power loss.

[@bingosunnoon9341]

Did you explain what transistor bias is and why we use it?

[@talideon]

Biasing is the process of setting up the operating conditions of an active device. Many such devices require a steady current/voltage to operate correctly, so you need to set up networks of resistors and caps to guarantee this. If you look up a datasheet for an active component, it'll give you graphs indicating the quiescent point: this is the point at which the device is _operating_ but treats as no signal. For instance, you might need to supply the base of an NPN BJT with a minimum current, and you'd use a voltage divider in many circumstances to do so. That explanation is a _gross_ simplification though, and is just about biasing a single pin on a device. You might need to look at an earlier video for one that goes into proper detail.

[@MegaDrna]

Hello I have a question regarding input impedance that you are speaking in the video, could someone explain the me the "impedance" therm, I am new in electronics and I can not understand the therm.

[@adamclark5065]

Alin Dragan Impedance is similar to resistance and is calculated for AC circuits like resistance is for DC. It's how much the circuit "resists change" and is calculated in terms of Ohms.

[@primetrader5062]

Am I right that if in emitter-following configuration you bias the base to the point where transistor goes into saturation at the emitter you will get Vcc?

[@xxmountaindewxx7893]

oh my gosh i got it now! god bless

[@jamendony589]

Nice tutorial very clear thanks sir

[@israelortiz7147]

Very good work......

[@tamarkan]

did you just count "common emitter" twice?

[@IsaacC20]

Common emitter is the more common of the 3 (common-base, common-collector, common-emitter)

[@tarlingkhongwir9467]

Sir, if you say that vcc is that much, and Ic is that much, why don't you show us the calculation how much Rc, Re, Ce, R1 and R2 should be.

[@crocellian2972]

Great. Thank you. Yes I see problems. Teaching electronics to kids with Arduino cancer is so important, I don’t care. Keep it up.

[@abfig78]

I always remember NPN as "Not pointing in." Idk. It works for me.

[@Popart-xh2fd]

These circuits are classic in all electronic books, so is nice to have lessons about them on the youtube.

[@carmelpule6954]

At 20.33 you say that the output impedance of the emitter follower is approximated by the output impedance of the source divided by Beta. Well what if the source is a current source? well I would rather you have taken into account the base biasing resistors too. Still you did say approximately and you do know what you are talking about. as a very practical man. I am glad that you like the BJT for its non-linearity as this can achieve more functions, as multiplication hence modulation and demodulation. I like your informal style of teaching, good man.

[@jasonfoster305]

Put your cap on the marker between ramblings, it'll help.

[@emsiiz]

I love that even transistor choice is biased!

[@coloradowilderness3139]

About pics left side of the board ?

[@MILENEO3]

This guy started the basing in reverse, normally you establish first the Vce Q point and the collector current by setting the Rc and Re then you calculate the required base current and voltage with R1 and R2 , you can make tradeoff and calculations adjustments on Rc and Re depending on how much voltage gain you want and your Q point, I think that this explanation is highly confusing for the viewers.

[@TheRokkis]

"we'll just say is V+ over 2, which it's not necessarily ever going to be" *flashes EPIC trollface" I just lol'd too much. Btw thank you. I don't know if it's past 3 weeks of trying to understand electronics building up, or your explanation, but I think I'm actually starting to get things.

[@Infinitesap]

could you make a Pete's play list?

[@Ashishcsify]

Sir please tell in TTL logic current input is emitter but in NPN transistor current flow from collector to emitter meant emitter is output please teach on that Thank's

[@gfodale]

transistors, biased for amplifiers are analog, not TTL.

[@utsavmajumdar2747]

great teacher

[@DillonStrichman]

you look like michael keaton and your videos are good thank you michael

[@therandomchannel9226]

Not so easy to understand as he is mixing up things!

[@filipsebik6138]

Johnny Depp making teaching us how to bias a transistor? Awesome

[@vinetta]

Schematics?

[@frankreiserm.s.8039]

How can you know so much about electrical engineering while having to raise a family (I saw your child's photos). I am 60 and I do noyhine except study the sciences (I clean house while memorizing cards of formulas). I like your littie friend on the board. Frank Frank Reiser Video/Audio Service

[@justcasey3678]

Voltage across the Base to Emitter on a silicon transistor is .7V and germanium is .3V. 2n3904 is a silicon transistor.

[@snnwstt]

That is fine if you work with 10V, but if you work with 2.5V, you would likely consider (or be aware) that a silicon diode can have its forward voltage from 0.55V to 0.85V with the later more frequent for integrated circuit and around 0.7 for discrete component. But a little bit as for LED you would see that the "knee" is FAR from being well defined value, anyhow.

[@christianimbert6976]

If Ic = 5mA and HFE = 100, then you want IB = 50uA ; hence IR1 should be 0.55mA and not 5mA , which means R1 = 13,5k Ohms, not 1480 Ohms.

[@UOIT_ENGR_Tutorials_Winter]

in regards to your marker, all you need to do is, after each time using it put the lid back on it. it gets dry without lid !!!

[@mohammaddawodi7484]

for your marker all you need to do is, to put the lid back right after each time you use it.

[@frankreiserm.s.8039]

Great! How would you use transistors, or perhaps an op-amp, for radio volume control? Enjoy my geology/science videos by typing in Frank Reiser M.S.

[@MrEkg98]

Needs better explanation of why the resistors in the circuit are what values and why.

[@davidluther3955]

YOU NEED TO CALCULATE r'e FIRST FOR THE COMMON COLLECTOR CONFIGURATION AND,MULTIPLY IT TIMES BETA TO GET IMPUT IMPEDANCE OF TRANSISTOR.

[@pirateman1966]

Its hFE not hfe. hfe is alph and used only on AC signals. For biasing, hFE or Beta is used.

[@frankreiserm.s.8039]

Remember that, in order not to destroy your transistor, add a diode (+ terminal toward Vcc ) in series with a 0.001 microfarad CD capacitor in parallel with your collector . You are brilliant. Thanks. Frank

[@EJAVAM07]

This guy's voice reminds me of Mandarin; his tone goes all over the place.

[@castroh]

Uhm i think this video has lots of confusing info, vin and vout doesnt act on the transistor voltages, thats why engineers use capacitors to isolate the input signal from the DC biasing

[@8bits59]

This guy is the alton brown of electronics. Good video. Needs more clarity, though.

[@aladaris]

"Uncommon Base" [rimshot]

[@grantgardner6747]

are you sure that is the direction of the I ?

[@rosegardner9660]

No. Is it?

[@kateiry4719]

13:00 "It's going to turn that sucker on" Wait he's right, that *IS* a sucker some way the other

[@SaadouneZinji]

Have you really studied electronics or is it just a hobby?

[@thusomontshiwa5645]

thanks ey

[@jonayamaha3215]

18:49 Thats a nice beta

[@PlantsGrowing]

1µA times 100 is 100µA... 2:01

[@thecoinmagician]

I don't think anyone should take the piss out of mr spark fun , this guy is no dummy. In electronics there is always some clever ass who claims he knows the subject better than the "other guy". A sort of boxing match of who knows more than the other guy. I studied this subject for years and i know nothing compared to mr spark fun.

[@inkblot777]

"In electronics..." "On the internet..." Unfortunately.

[@antoniolepe4670]

Common Emitter not Base

[@TheRangeControl]

Dude... I truly appreciate your enthusiasm. However, as a "Noob", I NEED for you to speak more evenly, and use punctuation pauses. I am not stating this to be judgemental. Your enthusiasm would make you an awesome instructor. But, for those if us who need this, you are throwing terns and theory at us with a consistent flow. With no pause for us to digest, you may as well dump a steady flow of water in our mouths without pausing for us to swallow. Together you and I are spilling information all down my face and the front of my metaphorical shirt. PLEASE, consider these factors and re-explain with another video, which I am sure will be amazing. Please be merciful to your Noobs. :-D

[@firemanleeman]

Can we get rid of the annoying background music? Very distracting.

[@coloradowilderness3139]

May be you have crossed the age. People below 35 like music hard soft...

[@jaran035]

You made a mistake. If you are supplying 9volts dc, then you couldn't have 5.1 and 4.5 volts respectively as you said it was...

[@snnwstt]

Why not? Vcc=9, Vbb=5.1 and Vee=4.5 seems possible to me.

[@billybob-392]

you seem to have confused yourself more than you confused me bro ….

[@chaddonschaddons7084]

I'd say terrible but as this appears to be a hobby for you, enjoy.

[@jurotech]

First..What is biasing?

[@Daitomodachi]

Biasing is setting the voltage to the gate/base of a transistor so the transistor can behave in a certain way. E.g. for power electronics, typically setting the gate voltage of a MOSFET at 12-15V saturates the MOSFET making it ideal for switching.

[@Daitomodachi]

Lundistani Shitteater For something like that, I would not bother using an NPN transistor. Typically the current flowing through an npn transistors depends on the base current going into it. In fact, BJT are typically good for current amplification and voltage amplification. My suggestion is to switch to a mosfet and use pwm to control the brightness. Before doing that, I would first find out the current the light bulb is consuming as it will affect the mosfet selection. Hope this helps. Good luck!

[@reggiebacci]

Lundistani Shitteater Are you sure it's not the voltage drop across the p-n junctions (0.6v ish)? With bulb connected directly to 6v battery; Power = 6v x 250mA = 1.5w. With transistor however - Power = 6v - 0.6v x 250mA = 1.35w

[@reggiebacci]

Lundistani Shitteater The hFE of a 2n2222 is usually around 250, so to get an emitter current of 250mA you'll need a base current of about 1mA. Try connecting the base directly to the 6v rail or use a low resistor

[@reggiebacci]

Yes. If you had 1mA base current the maximum emitter current will be 75mA. A 2mA base current will be 150mA. Max emitter current = base current x hFE within the limits of the transistor.

[@stefflus08]

Video looks good so far, but it's really bugging me when you write a zero with Ø. -Stop it. If you want to discern the zero from the O then use a horisontal line inside it. The Ø is a real letter in Norway and Denmark, besides it is the international symbol for diameter.

[@Nocturnes1984]

I hope for $3.ØØ a minute you are a bit friendlier to your clients....

[@valos_cor7842]

Wow, a LOT of Americans do it that way. Pete is not Norwegian or Danish, and to expect him and a lot of other people to change their ways just because you aren't used to zeros written that way is pretty entitled.

[@snaprollinpitts]

dude, I know you know your stuff, BUT you need to work on your explanation, do each configuration at a time. to do all of them at the same time is a mess!

[@mr.jaydeepmakwana7457]

You are Er. jack sparrow

[@JohnSmith-ed1sr]

This guy has a job?

[@beetlebee8656]

put the cam straight...how abt a smart board!

[@Nocturnes1984]

How about you donate a shitload of cash to this guy so he can buy a "smart board". Be kind

[@practicalsoftwaremarcus]

funny ;P

[@danieljoseph6404]

You kinda look like the birdman haha

[@jbuddyman]

Thanks Johnny Depp

[@DocuDramatic]

You're a good explainer but you beat around the bush so much. For example you go: "If you think that electronics is an exact science, brother (or sister) you might need to think again". You go astray like that a lot... Why try to defocus the viewer from the subject matter? This would be so much better with less clowning and more continuity. This stuff is complex enough so why make the viewer wonder all the time "What are we talking about now?" Friendly advice.

[@1959Berre]

You need some stability in your explanation. First get a marker that does the job, it is distracting.

[@jomelsagsagat4020]

Are you talking about stability to changes in Beta ?

[@AlpNewYork]

I dont know whats going on here everything is all over the place

[@acmefixer1]

I stopped after less than 3 minutes and the second mistake. I didn't like his blase' presentation and mistakes, obviously. 😕😕😕

[@koggism]

Most dreadful explanation of all time. 2mA base current hahahahahah

[@jomelsagsagat4020]

Paul H lol should be in the micros

[@dan-ignacekafwimbi6551]

you are spoiling people Mr. leave and take a seat

[@vinitshandilya]

Johnny Depp teaching basic electronics! 😉

[@leaderbiogano9362]

He explain science, but his style is like a vlogger. I did not understand. He should learn from GreatScott, or Mr. Collin.

[@jjay11a]

HAHAHA!!! this guy has never taken an electronics class in his life, when people talk to much is cause they dont know what they are saying.

[@gnuPirate]

+Jose Alfonso Hello Jose. I find Peter's videos to be useful and helpful. Have you made any videos or other material that are more useful and helpful than these ones?

[@snnwstt]

Unless you know him personally or have seen his very detailed C.V., you can't tell and that is a claim without proof. He is a good communicator, and for that, the video is there to support this claim.

[@excitedbox5705]

This has to be the worst most confusing video I have seen yet.

[@robfrei6375]

Wow, this is really bad.