#356: Back to Basics: the Emitter Follower, or Common-Collector Amplifier

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Inspired by a friend's question from the book "The Art of Electronics", here is a back-to-basics video on the BJT (bipolar junction transistor) Emitter-Follower, or Common-Collector amplifier. Some useful video links for background on some of the topics presented are:
Bipolar C-E amplifier biasing:
Comparing Common Emitter, Common Base and Common Collector amps:
Common Emitter design hints and tricks:
Vbe Multiplier - and push-pull amp biasing:

Notes from this video:

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The Art of Electronics is TERRIBLE for learning about basic electronics. Older texts from the US Navy are EXCELLENT for explaining how these circuits work.

chuckcrizer

The oscilloscope probe as a pointer - original!

cnccontroller

Sir, your video's are outstanding, I know of no one who can explain difficult subjects (for me they are) so well. Your drawings are so helpful! Thank you for taking the time making these video's...

erikderuiter

Eternal life to this man, if you were on the Titanic the entire crew would agree to give you a boat just for you.

ClaudioGabrielCastillo-uqhj

Great video Alan, I’d have gone the EE route if you were one of my early teachers. Really enjoying finally understanding a lot of details my young mind didn’t get, now years later making sense through your videos.

MD-sjdn

45 years since I did this at collage. So nice to be refreashed. I now understand better than I did back then, Thanks.

PeterGagen

In order to simplify calculation the emitter current in 5:09/21:33 as approximated as Ie ~ β*Ib where as the the actual Ie =(β+1)*Ib, but even that does not accoumt for leakage current Ie]bo
The point I a trying to make is that junction transistors are complicated so calculations such as shown in < #356 Back to Basics > are REQUIRED to get reasonable answers .
A power transistor such as 2N3055 has βmin = 5@ Ic=10 amp ; in that case the Ie Ie =(β+1)*Ib is REQUIRED !

martinmartinmartin

Another superb video, Alan - thanks! I think it'll become one of your classics. That question about clipping, from The Art of Electronics, has caused a lot of head-scratching. Much better to see it solved as you've done here, by equipping people with the background, than by addressing just the question in isolation.

whippoorwill

"Basic" turns into "Simple" (kindof) once a good teacher such as you explains it. Thanks for sharing and the good paper- and camerawork

tav

Your Illustrations look like it straight out of the Engineer’s Notebook by Forrest Mims. Also, Great Video !

X-OR_

When I was teaching at a local university I did a session "proving" that an emitter follower could have a gain greater than one. Use an audio frequency that can be measured by your standard VOM of the day (20, 000 ohm/volt). Measure the base signal, then move the meter prob to measure the emitter signal. Voila, the emitter is greater than the base. This is an "illusion of measurement" When you read the HIGH impedance base, you load it more than you would when you move the probe and read the LOW impedance emitter. This is a well-known phenomenon in the industry but it's a wonderment to a new student.

utoothheartyeight

Man, missed these back to basics videos. Thanks!

HM-Projects

The way you explained in/out impedances was so delicious I could almost eat it. Well done. With love and respect from Shiraz.

johnkyingilisi

I haven't got to The Art of Electronics yet, I'm still studying "Electronic Devices" by Floyd. Maybe when I'm finished with Floyd I'll move on to A of E. Nonetheless, this video is right up my ally. ; )

reedreamer

Probably your best video till now. Really appreciate your in depth explanations.
Especially I finally understood your definition of impedance. Great with the math and circuit explanations.
Thanks a lot! :) I hope you continue soon.

Infinitesap