Why the emitter follower could decrease the feedback?

[katrin]

+emitter follower +feedback

I read that sometimes people use emitter follower in between different circuit stages to reduce the feedback, I wonder why the emitter follower could achieve that?

 

[Davood Amerion]

emitter follower used where we want to have amplify signal current, but not signal voltage.
in other word it used for buffering, and have high input impedance and low output impedance,
with voltage gain of approx unity.


Regards,
Davood.

 

[suria3]

As Davood said, Emitter follower is a circuit with high input impedance and low output impedance. It is used in between gain stages as to isolate the main poles that decide/degrade the bandwidth by the gain stages. As we know that EF has low output impedance, so that this low impedance when parallel with the next stage amplifier which has high input impedance, the total impedance will be even lesser. So, the poles at that point can be moved further up which helps in extending circuit overall bandwidth.

At the same why people say it is reduce feedback, we know that as gain reduce the bandwidth will increase in common circuit, so the effective gain is reduced (a kind of feedback) at the output of the emitter follower.

 

[paulux]

I think......the emitter follower gain is close to one but is practically always less than one, so it decreases the effective feedback gain.