For an emitter follower the voltage gain is given by A_v=(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.
But I can't neglect the internal capacitances. I suppose that the gain changes with frequency.. I have tried to insert the internal capacitances in the model for the BJT (using the T model) but I don't know where put them. The only example that I have is the application of internal capacitances at the BJT common emitter (with hybrid-pi model) for the high-frequency..
Could you show me how to find the formula for the voltage gain of an emitter follower?
ps= excuse me if the formula that I have written is not immediately readable, I'll learn to use the system of this forum to add math formula