Hello, I have problem with input resistance of emitter follower. But first quick check: If I'm correct, equation for input resistance will be: where: Ok, that was quite easy. But the real problem I have with this: Question is the same - what is equation for input resistance? First problem is with two transistors. I'm not sure about this part of equation, but it's the best of what I've think of: But I don't know how to write the rest of the equation.