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## Homework Statement

I'm trying to find a relation for the voltage gain of an emitter follower.

For an emitter follower the voltage gain is given by \$A_v=\frac{r_o|| R_L}{(r_o|| R_L)+r_e}\$, where \$r_o\$ is the output resistance of the transistor and \$r_e\$ is the intrinsic resistance of the emitter. This result is obtained without considering internal capacitances of the BJT.

What should I obtain, if I do a graphic (modulus and phase) with the response of the amplifier to the frequency?

## Homework Equations

## The Attempt at a Solution

The formula that I have written on the top gives me only one value... so I think that I have to use one that depends on frequency, (and so in this formula have to "appear" the internal capacitances of the BJT) but I don't know how I can obtain it...

If I have correctly understood, the emitter follower needs to the T-model for small signal, but I have seen the internal capacitances only for a hybrid-pi model and for high-frequency. So I don't know how to go on. If you can help me, I'll be so grateful!