Topic 32: The Emitter Follower (And a major problem with this implementation)

In this video we derive the equations for voltage gain, input resistance and output resistance for the classic emitter follower circuit that is presented in all the textbooks. We also demonstrate why this particular implementation is not usable in practical applications.

[@amjadtrablsi4051]

amazing content 👍👍👍👍👍

[@Electronics4Guitar]

@@amjadtrablsi4051 thanks! 👍🏻

[@TekCroach]

Excellent videos... Anyway, a misconception has to be dismissed. Most people used to say input impedance of the subsequent section must match with the output impedance of the previous stage. Not always! You must try to achieve it if you want to transfer power (with power amps). In almost all other cases (where the signal is modeled by voltage), we are only concerned with the voltage signal. So, we should not try to match impedances; instead we must try to make the input impedance larger as much as possible. It is impedance bridging, not matching. On the other, common collector is a very useful circuit!

[@Electronics4Guitar]

I agree completely. For small signal and low power amps high input impedance is most desirable. Impedance matching is more important in high frequency applications. Thanks for the comment! 👍🏻

[@davidluther3955]

EXCELLENT PRESENTATION!THE GRAPH COULD USE LINES ON IT.WHAT IS THE FORMULA FOR THE CURRENT GAIN FOR THIS CIRCUIT?

[@Electronics4Guitar]

@@davidluther3955 this equation works for any amplifier:
Ai = Av(Rin/RL)

[@davidluther3955]

@@Electronics4Guitar I ONLY WISH I HAD THESE GIFTS WHEN I WAS STRUGGLING TO LEARN ALL OF THIS IN COLLEGE MANY YEARS AGO.

[@Electronics4Guitar]

@@davidluther3955 I wish I had recorded the lectures I gave at the college. If I can find some I might post them sometime.