#114

[@boonedockjourneyman7979]

Ever time I try and teach this part of BJT applications, I end up showing this video. Students really get it.

[@w2aew]

That's so nice to hear - I'm very glad to know that my work is helping people!

[@esvna]

That was 3 months of lectures summarized in 11 mins. Excellent tutorial!

[@Ghost572]

I know a lot of the online material on the internet sort of shows this isn't understood and just adds to the confusion, or essentially leaves you to have to fill all the gaps in before you can fully understand what is going on.

[@Zapgod]

Bro they teach us this in 3 days then test on day 4

[@ChupoCro]

@@Zapgod At university? Not really I think :-) At university you learn for 3 months only what is happening at the P-N junction when transistors are not even mentioned. And when you start learning the transistors then you learn these configurations *in details* - certainly not in just a few lessons.

[@Zapgod]

@@ChupoCro in the navy, this is how they train

[@anthonycalia1317]

You are a natural teacher. You have the unique ability to transfer all of the key information in a manner easy to understand and to the point. Excellent!

[@edwardbass9255]

Everytime I think of an electronic topic I need to better understand, I search your channel first. You are an awesome teacher. Thanks for all you do.

[@jimadams2473]

Seriously, this is the BEST transistor explanation on the web. EXCELLENT work!! Thanks.

[@caribbeansimmer7894]

It's the best I've seen as well. It's crazy how many persons make it more difficult than what it is.

[@Radionut63]

Now this is teaching! Thank you for uploading! :-)

[@AppliedScience]

Another great explanation! I had never thought about cascode amps like that, but it makes a lot of sense. Have you ever worked as a teacher/tutor professionally? You'd be the best!

[@hadireg]

Coming from Applied Science that's the best recognition one can have 🙂 Thanks for your great channel you're making the world a better place👍

[@Roy_Tellason]

Many years ago I ran across a circuit in a magazine (remember those? :-) that I just had to try out. It was a single transistor in a common-base configuration that allowed me to use a small 8 ohm speaker as a microphone. Worked well, that did! So that's not just "mostly RF"...

[@BenWard29]

Even 11 years later, this video is still a great resource. There's one issue I'm having, though: Everytime your phone dinged in the video I looked for my phone thinking I had a notification. The ding sound of your phone sounds nothing like mine- so I have no idea why I even think it's my cell phone. I guess I'm Pavlov's dog.

[@billbates7810]

A very good video, even down to the camera tracking your pen as you moved from circuit to circuit… very impressed! God bless, Bill.

[@jimmylightfinger1216]

Succinct and well paced. Nice to have the book and lab in combo...separate classes often have a different feel and temperaments especially when lab partners have not done any preparation.

[@opalprestonshirley1700]

Excellent presentation. I learned all of this over 30 years ago it is good to see someone teaching this as a needed refresher for this old man.

[@OctavMandru]

Alan, 9y later I keep rewatching your videos. The best, most concise explanation. You are possibly on the best teachers I ever had. Thank you, Sir

[@igroundspq-niverse8493]

I realize this was done several years ago, but is by far the MOST LUCID explanation on the three common configurations. Thank you so much!

[@justinmcginty101]

Excellent instruction. I'm studying for the Advanced Amateur Licence (Australia) right now and videos like this one are a great help. Thank you very much.

[@dennisvirmudes366]

This was a great tutorial for transistor amplifier connections. I never expect it open my mind to deeply understand the connection and the effect of changing the value of resistor as you did in common emitter. Your 11:08 is very valuable for me.Thank you very much

[@mdesm2005]

Very nice. This 11 minute video probably took you 11 hours to prepare. Impressive. Thanks. I like "rules of thumb" for using one configuration versus another. Please consider comparing BJTs to FETs (to Op Amps?) in the future.

[@Ragingwasabi9000]

The content u give is so thorough and wholesome. solid lesson, thanks so much!

[@absurdengineering]

For an emitter follower, it helps to stabilize the collector current with two additional transistors. That way the B-E voltage is constant, the gain is closer to 1, and the already low distortion is even lower.

[@1ebutuoy2]

Great video! A common base amplifier is also great as a preamp for a low impedance microphone. Low noise, high gain.

[@overengineeredinoz7683]

This video explains the concepts so clearly and concisely. Perfect really.

[@bunkie2100]

Simple, elegant and efficient. That’s about as good as an explanation can get. Well done!

[@21thTek]

love your videos, always learned a lot in a short period of time, winner tutorials !!

[@kparasu12345]

Very good ... please post for FET & MOSFET also

[@rawtuber]

please do!

[@hadireg]

awesome demo, especially for the common base. Thanks fot the great content sharing!👍👍

[@benthere8051]

The common base is the hardest for me to employ.

[@현정호-h4d]

Best explanation , i think yes, thanks for making this video

[@zarserz]

Thanks, love your videos. By far some of the best electronics explanations/tutorials on youtube.

[@JerryBiehler]

Anyone else keep checking their email as the video played? "bing" - looks at iphone, nothing there...

[@anurasenarathna1703]

Great video. Very nicely explained.

[@anurasenarathna1703]

Great video. Very nicely explained.

[@starlight8260]

Wow, yet another superb video..simply the best set of electronics tutorials on KZbin. Hats off to you sir!

[@UberAlphaSirus]

I should comment on your videos more often, as you are awesome. You really fill a niche nobody else covers as well and concise as you do I was wondering where the term "common" originates for these setups and also so I am never confused again, what are all the other names given to these circuit that mean the same, such as emitter follower. Thanks again.

[@beaconing7689]

I don't understand this Common Collector amp, when i measure the output using Oscilloscope there is no voltage gain, but when i measure the output using multimeter there is significant gain from 1V to 9V! Its confuse me 😕 Can someone please explain to me what's going on?

[@w2aew]

A common collector amplifier does not have any voltage gain, but it does have current gain. It is most commonly used as a buffer amplifier - to take a signal that can't drive a low impedance load and buffer it so that it can drive a low impedance load.

[@marekmosat7176]

I just do not have a words to express how I love your videos. Thank you Sir.

[@chrispychickin]

Thanks very much for this video, it was really insightful and helped my understanding of these circuits a great deal. I think it would be great if you were to scan in the pages of tutorials like this, and post them online, so that the viewer is able to "play along at home" and have them for further reference. I for one would really appreciate it! Thanks for the great videos, you're an excellent teacher and have made so many concepts make more sense to me! peace chris

[@soulmate07748]

Excellent explanation and tutorial!

[@IIeTpOc9H4uK]

Perfect video! THanks you a lot. It is very clear and I like how you showed the example on the oscilloscope right away.

[@W1VLF]

Hi Alan, Thank you for this video, Actually all your videos have been extremely informative. I am most interested in the common base configuration. The project is 2 build a preamp for a wide band single turn loop antenna. Wide band being 20 KHz to 20 MHz or so. The single turn loop of about 1 meter in diameter is a low impedance source, actually it changes across frequency I believe. So I was investigating common base amplifiers and found your video. Can you please tell me how to optimize, make the lowest input impedance for this type of amp? Originally I thought it had to do with the emitter resistor but now I see that it is a function Re? So is Re device dependent? Or can it be adjusted by the resistor values? Thank you again for the great videos. I will eventually watch them all W1VLF

[@w2aew]

The effective small signal emitter resistance (Re) is a function of the collector current. It is also 1/transconductance (gm). Since gm = Ic/26mV (at room temp), then Re = 26mV / Ic (at room temperature). Thus, higher collector current gives you lower Re.

[@joshuamartin4837]

Brilliant! Thank you so much.

[@maurosobreira8695]

Excellent intro tutorial on the amplifiers, Alan! I got a question on that: On the cascode amplifier, the signal passes through the common emitter amplifier first and then passes through the common base...so it seems that the bandwidth reduction effect is still there on the first stage. Is this effect reduced just because the voltage gain (Av) for the common emitter is minus one on the cascode configuration, or something on the common base prevents the inverted signal from being coupled back by the capacitor effect and reduce bandwidth?

[@w2aew]

mauro sobreira It is because the voltage gain is reduced to -1 on the common emitter stage. This minimizes the Miller Effect. The Miller Effect is the multiplication of the C-B capacitance by the voltage gain. Since the magnitude of the gain is unity, the C-B capacitance doesn't get multiplied like it would in a single common emitter gain stage (without the cascode).

[@maurosobreira8695]

***** Crispy clear, Thanks!

[@rolfts5762]

-->Thank you very much for very very nice interesting and educational videos. 'This' video in special, contributed a great deal for a big level-shift for undersigned. Previously only used and known about the ordinary common-'emitter' configuration. ...Now the common-collector(/emitter-follower) config I would guess have a beautiful potensial in own designs. Looks like OpAmps and com.coll.'s(perhaps driven via a driver first?, if current-sensible), seem to have very nice potensials in elelctronics. Again, thank you Alan. br, from Rolf scandinavia, norway. La3epa -thoughNotSoMuchActiveOnHf..for the moment. (Hope one day perhaps try make a hf-contact with you, when practical-conditions for it allows from here later in the future.)

[@snaprollinpitts]

whiskey two alpha echo whiskey,if you are not an electronics professor you sure could have been. as always a perfect tutorial right on the money!!!! thanks

[@w2aew]

I am not an electronics professor - I just play one on KZbin! Ha!

[@snaprollinpitts]

***** I am very grateful that you do, you have taught me so much already. I really like you tutorials, I learn more from them. thanks

[@lowellyates7404]

I wish I had him Navy Electronics Technician School years ago.

[@josephwarren849]

Great video very helpful, more like this would be grate.

[@tunicana]

Beleive me, you have a gift to explain electronics.

[@aicisha]

Hi, can you make a tutorial on how you can tie up multiple CC, CE and CB to make a decent small signal amplifier?

[@ismailcemtuzun6535]

amazing explanation ! thank you

[@hanndoddi]

Thank you for a very well made tutorial :) Are those glossary notes you are using accessible somewhere?

[@bassemkhalid6876]

An Excellent Tutorial. Thank you very much. Keep the good work on and if you have some time for different types of multivibrators , it would be really good. Thanks in Advance.

[@phanimalladi9270]

Ideal.Best way to learn by practical approach, lesson to future. Thank you SIR.

[@PauloConstantino167]

and you are a common conman

[@theviking6593]

thank you so much for this video i love the way you explain how CB,CE,CC works. nice job BRAVO

[@trialen]

You are an uncommon teacher.

[@EdwinFairchild]

i have a similar setup except with the addition of a coupling cap at the output , but for some reason my waves are slightly more out of phase and about a voltage difference in Vpp , but once i crank up the frequency they line up a lot better and only about .1 volt in difference Vpp. im assuming it has to do with my capacitor values and perhaps cut off frequency, but im pretty sure my values are right and should work for the frequency ranges i want basically 120hz and above. my AC source is 10Vpp @120Hz and above. coupled via a 4.7uF.... My collector is @12Vdc I have two 1.2k resistors giving me about 5.9 volts at the base .. my emitter i\has a 470ohm resistor and from my emitter i have a 47uF cap.... at 120Hz i have a good amount of phase shift, and about 1v difference in the waves... at 1Khz everything lines up pretty nicely... how come? I would expect everything above the cut off frequency to line up nicely

[@w2aew]

One way to verify if the capacitive reactance of a coupling cap (or decoupling cap) is causing the issue, try temporarily placing an identical capacitor in parallel with the one in the circuit. If you see a difference, then you know that the value is a little too low for the frequency in question.

[@RobeenaShepherd]

Just a quick thanks for your really helpful explanations and demonstrations. I understand more in a 10 minute video from you than hours of formula obsessed textbooks. :)

[@ornithopterindia]

👍Thank you sir.

[@otimatra]

Awesome tutorial. thank you so much

[@ronaldlijs]

VERY VERY well explained, it's like magic. This directly relates to schematics I've seen for RF circuits and it makes it easier to understand WHY the different setups. Keep them coming Alan!!!

[@ToltecMerc]

At 5:50 you say Common Emitter but I think you mean Common Collector. Thank you for a great tutotial.

[@w2aew]

Yes, you are right. Good catch. At least I properly stated it as a Common Collector amp in the rest of the segment.

[@1959Berre]

+ToltecMerc I just wanted to make the same remark, since I checked, I noticed you already did mention it. Good catch :)

[@Gw0wvl]

I think he just said that so as to make sure you were paying attention :-)

[@bluehornet6752]

@@w2aew I noticed it too--but you can read the words "Common Collector" on the page (because you just finished talking about that form of BJT), so it's pretty easy to follow what's going on. Awesome video though--really helpful to see the signals: Common emitter (inverting) vs the other two (non-inverting). That's incredibly helpful, so thank you very much for making this video!

[@uuyoubaan4uuyou829]

I​ got​ terrble grade on​ my​ electronic​ course​ 20​ yrs​ ago.​ I​ wish​ you​ were​ my​ teacher​ back​ then.​ I​ would​ have​ love​ electronic.

[@bobvincent5921]

A good refresher course,amazing what I forget over a weekend.

[@SheikhN-bible-syndrome]

But what does a circuit look like for a BJT like the 2sc5200? I can't see it having those small resistors on the emitter and collector legs and somehow pull enough power to produce 10 to 15 watts so I guess my question is what does a big power BJT output stage look like? And how do you make it to where you don't need DC blocking capacitors? Because if the amp had 25 to 50 watts of output it would require pretty big capacitors on the output and you can't use poler capacitors if I remember correctly? . So I'm just all over the place confused

[@jeditoto3441]

Hi Alan, - could you explain the role of Emitter resistor (degeneration or "negative feedback") in a video - this confused me a lot when started learning about the different configuration. I am sure many people would benefit from this :) - especially with the great way you have of explaining things!

[@shaqywacky]

Great video! I just learned this in class it it was awesome to have you wrap it up.

[@teberer3246]

With class C RF amp, can you explain how it can be used/ modified to an AM or FM transmitter, BTW your tutorials are very clear and easy to grasp.

[@waynegram8907]

Common Base is a current amplifier and the common collector AKA emitter follower is a voltage amplifier and the common emitter is both a current amplifier & voltage amplifier? I have seen a Common base configuration being used to boost the current for digital CLOCK signals. Common base configuration have the collector as the input which boost the current not the voltage of the clock signal to the base pin as the output.

[@chrispychickin]

I second this! I'd love to have an in depth explanation of input and output impedance. keep up the great work! peace

[@microflite]

Great video. Minor error you might want to fix with a caption - at 5:51, you said common emitter instead of common collector. Thanks for the great series.

[@jebsaekam]

I'm confused about the cascode configuration. How does it negate the bandwidth limit of the common emitter? The miller effect is still there right? Doesn't it need to run through the Common emitter first? I initially thought was that you said something wrong and that a common collector feeding a common base would make more sense. Great Video as always.

[@user-su5sq5ib3i]

Hey Allan. as you know Ive been in college and we are finally working with bjt transistors. In a common emitter isnt the AV gain rc/r'e because re is bypassed with the cap. and also the output impedance of a common emitter is usually low so that most of the signal gets out to the load?? All the best ve1qet

[@freon500]

I'll figure out some way of attenuating the input signal to less than what either of my two signal generators produce which is about 1/2V minimum. I'd like to be able to attenuate into the millivolt scale. I'll also try tweaking the gain and the bias. Wish me luck. Thank you!

[@superblunt12]

Hi Great video I just want to make sure I got this correct all of these circuits take an ac signal and amplify it to a dc biased signal so the signal will be seen on top of an dc signal. If this is correct I would like to know how to you get this signal back to ac?

[@chuckvanderbildt]

Clear, concise and well structured explanation. I am impressed, thank you for making these!

[@uuyoubaan4uuyou829]

Hi I would like to ask about the type and value of Capacitor. How can we come up with value of Capacitor? What type should it be? Can we use electrolite capacitor, saftly?

[@FungSit]

Great tutorial! Thank you.! Can you also make a video about multistage amplifier? I have trouble coupling CE and CC without having loss in the signal. Tried making the Rin of CC larger by increasing RE or biasing resistors, but then it's gonna eat up the voltage of CE, also tried making Rout of VCE smaller, but it depends on RC which I need its value to set the gain.. so many conundrums, it would be much appreciated if you can make a video about this designing thought process and strategies.

[@HansunLee]

可惜我不大懂英文，否则应该可以解答你一部分疑问。

[@FungSit]

Hansun Lee 我試著翻譯我說的內容成中文，因為這些中文詞彙沒學過。我的問題是在兩個放大器的銜接，如果前一個放大器的出口阻值太大，後一個放大器的入口阻值太小，那麼信號傳輸過程中就會丟失，CE的出口阻值沒法減少，CC的入口阻值也沒法增加，因為牽一發動全身，我不想改其它參數。

[@w2aew]

That is a good suggestion for a video. It is always a balance of several parameters. If you can AC couple the signal between stages, some of the constraints are removed since you and set the bias point independently.

[@jonsanford0]

Yuji Naka The Google translation of this makes sense. Like explaining a different way. import and Export resistance sounds cool.

[@FungSit]

***** Now I'm trying to figure out a place to put a bypass cap. I biased them separately anyways. Thank you again for the nice tutorial.

[@tonybell1597]

Another excellent tutorial, still not clear about the common base amplifier though, not sure I understand how the transistor works by connecting the signal to the emitter.... Time to hit the breadboard!

[@marcisberzins]

In Common Emitter amplifier configuration it can be seen on scope that when bypassing the Emitter resistor along with huge gain increase there is also more signal distortion, as it should be. Thanks.

[@CoolDudeClem]

I've never heard of a common base amplifier before. Common collector and common emitter I already know, but not common base so I learned something today.

[@harrypehkonen]

A "Capacitance Multiplier" is common base, but with the input and output swapped?

[@davidcole6236]

Beautiful! Your vids are top shelf! That must be a Tektronix scope (my all time favourite especially the older ANALOGUE beauties, of which I have a few), but which particular model is yours? It looks like a 2000 series, like my 2465, but I'm not certain. Cheers, Dave

[@w2aew]

+David Cole You can see the model number at the beginning of the video - it is a 2467, which is the same as the 2465 but with a special CRT (called a micro-channel plate CRT, or "BrightEye"), which has a very fast writing rate.

[@waynegram8907]

The input signal level is what causes the transistors depletion area to either be narrow or widen. The input signal level is opening and closing the transistors depletion area?

[@jebsaekam]

I think it have it. More investigation will be done on my part. I may clarify more later. Thanks again.

[@FF7824]

Very well done and informativel. Thanks. 73

[@joblessalex]

Thanks for the tutorial! This is going to help me a lot designing my amplifier.

[@thecreator6381]

What is the transistor number 2n3904 ?

[@w2aew]

Any common NPN transistor like the 2n3904, 2n2222, etc. can be used in these examples.

[@unitedelectrician4334]

Thank you for the video!! Great job

[@uvatham]

00:28 Common Emitter 03:55 Common Collector 06:10 Common Base

[@gazzacroy]

a really helpful video. you explained it really well. cool :)

[@Pwaak]

I appreciate and enjoy this tutorial very much, Thank You!

[@solomontan1524]

Hi w2aew, could you explain what the equations mean at 2:50 ? The only thing I recognize is Ic which is collector current. I guess Rc means the resistance of the collector circuit (ie. 680 ohms) but that's all im able to figure out. What do re, gm, Vt etc mean? What's A in the eqn below? What does it represent? Is it A=(Rc/(re+Re)*(gmRc) ?

[@w2aew]

Yes, Rc is the collector resistor. The remaining parameters (re=small-signal emitter impedance, gm=transconductance, Vt=thermal-voltage, etc.) are all parameters used for computing the small-signal gain characteristics, and come out of a simple model for the transistor. The parameter A is the voltage gain. These parameters are explained a little more in a few of my other videos: Common Emitter amp gain and frequency response: kzbin.info/www/bejne/hJrdo62IgLakf6s Common Emitter amp design tips: kzbin.info/www/bejne/jIi8Y4qHmLB9nc0

[@mohammedkhaled2456]

Sir , why is it called common collector where the collector isn't common ? It resembles the common emitter except that the load resistor is in series with the emitter

[@w2aew]

It refers to the "common" terminal of the transistor with respect to the *signal* being amplified. For Common Emitter - the input is the base and output is the collector, thus the emitter is the "common" from the signal's standpoint. For Common Collector, input is base, output is emitter, and collector is "common" from a signal standpoint (via decoupling caps, etc.). The "common" terminal is the one that "doesn't move" with the signal - i.e. a reference point.

[@mohammedkhaled2456]

+w2aew oh I see . That means that the point which we don't place the input and output signals across is the common one .

[@w2aew]

Yes, you got it.

[@mohammedkhaled2456]

+w2aew Sir , I have read that the output voltage across the load resistor in the common collector transistor is approximately 0.7 volts less the input signal due to the emitter- base voltage drop . Is that correct ? And one last question sir , in the common emitter the output voltage is taken between the emitter and collector not across the load resistor while in the common collector the output is taken across the load resistor itself . Is that correct too ? And sorry about asking so much questions

[@w2aew]

The output of the common collector stage is about 0.7V lower in DC offset only. The peak-peak amplitude should be nearly the same (basically unity gain with a DC shift). In the common emitter, the output voltage is generated across the collector load, but the voltage certainly can be taken as the voltage between the collector and ground (since the supply voltage and ground are essentially the same from the signal's standpoint).

[@Avionics1958]

who in a right mind put a dislike ??? you don't have a clue !

[@Oliver615-b9b]

good day sir. i am a student at a university. now i have a report on TRANSISTORS AND AMPLIFIERS: power gain in transistors, voltage measurements in transistor circuits and phase relationships in common base amplifiers, common emitter amplifiers and common collector amplifier. these reports were assigned to me and i have a hard time in understanding how these works. now as a newbie in these stuff, i humbly ask for your help (if you have time and willing to help me) since you are a professional in stuffs like this. i would like to have you as an online resource speaker sir. i would like you to explain these to me in the simplest way you could. (minimized equations and the like) so that i could report it to the whole class with much understanding as you have. ill be reporting in class on September 22, 2014(Monday,Philippine time). i hope for your kindest and sincerest response thank you sir. :)

[@w2aew]

All of these answers are in this video. When I say that a particular configuration has a high voltage and current gain, then its power gain is high. When I say that its gain is inverting, that means it has a 180 degree phase shift. When it is non-inverting, it has a zero degree phase shift. A high input impedance an low output impedance implies a high power gain.

[@80sday36]

Hello Sir, that is the best teaching method I ever see. Anyway, what transistor do you used in this example and what is the maximum frequency that the transistor can handle? What transistors should I use to amplify small signal with the frequency range of : 17MHz up to 47MHz?

[@w2aew]

I just used general purpose transistors like 2N2222A or 2N3904 in this video. The maximum frequency of operation can be limited by a number of things. Usually it it the surrounding circuitry that limits the frequency response, and not the transistor's parameters like fT or Fmax alone.

[@user-su5sq5ib3i]

yes the dynamic impdeance is the emitter resistance at a certain temp with a certain dc current, we usually use 25mV/IE. 25mV being the quiescent voltage at 20degrees Celsius I would like to see you do a video on a swamped common emitter amplifier, have you done that yet? thanks

[@w2aew]

Yes, check out this video. It shows a swamped CE amp, and the same amp with the emitter resistor bypassed. kzbin.info/www/bejne/jIi8Y4qHmLB9nc0

[@ronkessler1599]

Hi Alan, do you have a video where you show how to calculate values for emitter by-pass and coupling caps? Having a hard time finding a succinct way to demo this to my class.

[@w2aew]

Some of the info might be in this video: kzbin.info/www/bejne/jIi8Y4qHmLB9nc0 For the emitter bypass, you choose a cap value that gives you a reactance that is 5-10x lower than the emitter resistor at the lowest frequency of operation. For the coupling caps, it really comes down to looking at the impedances on either side, and picking a reactance that gives you the coupling that you want at the frequency extremes.

[@xyloeye]

Yet another great review. Thanks, Alan.

[@lucaslucia7126]

Thank you! This helped me so much.

[@caravanken1]

OK, I confess I am a bit slow on the uptake so please bare with me; the voltage from the SG is 3VDC correct or not????

[@w2aew]

I'm not sure how you reached that conclusion??? The signal generator is providing a sinewave at about 100mVpp for most of the demos (a little smaller for some of the demos, such as the high-gain version of the CE amplifier, and for the CB amplifier).

[@Evmeister88]

Very helpful! Couldn't find a better video that broke it down like yours did. I searched your site, you don't have any more in depth videos on how the BJT works do you?

[@w2aew]

I've got a few more that use BJT transistors - like one that talks about frequency response of a common emitter amplifier, and another that talks about BJT differential amplifiers (long-tailed pairs), and more.

[@industrialdonut7681]

The emitter follower has to be the simplest one out of all of these, and yet I have literally the hardest time understanding it - how exactly/intuitively it has a low output impedance, how to drive a load with it, why my decoupling capacitor floats at 2 volts instead of bringing the waveform down centered about ground, etc

[@w2aew]

The emitter follower's ability to drive a low impedance load is essentially due to the fact that it has the benefit of a lot of current at it's disposal - the emitter current is Beta+1 time the base current, so it can provide a lot of current with little change in voltage (because it is simply a diode-drop away from the base voltage).