# Small signal model of emitter follower circuit

#### Phillolol

Dec 21, 2021
3
Hello!

I have been given the following task:

" Implement the emitter follower (efollower.ms14) with load resistors 100, 200, 500, 1 kΩ load resistance, and establish the gain for each case. (It should not vary very significantly). From this, deduce the output impedance. Hint, consider the output voltage and current as a Thévenin (or Norton) source, and use the gradient to find the Thévenin or (Norton) resistor. "

Here is the circuit:

Where exactly do the load resistors go?
Do I need to find the Thevenin/Norton equivalent?
If so, how would I go about doing that?

Thank you very much in advance!

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#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,769
Where exactly do the load resistors go?
The load resistor goes from the output (IO1) to gnd,
Do I need to find the Thevenin/Norton equivalent?
Hint, consider the output voltage and current as a Thévenin (or Norton) source

#### Phillolol

Dec 21, 2021
3
So if the output voltage and current are the source then RE is Rn?

Sorry, i am so confused with this task, i have been trying to look for information for 2 days and came here as a last resort.

Last edited:

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,769
What is Rn supposed to be?
What you need to do is find a representation of the emitter follower as voltage or current source, then attach a load resistor. See e.g. this discussion.

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