1. The problem statement, all variables and given/known data Here is the example along with the solution: What I don't get is what happened to the R_E value. So in this model does it neglect this value? It seems like R_E could be anything and you would still get the same model. I have another question, for this same example, it asks what is the max v_s that the previous analysis is valid? There are two criteria in which we have to look at, i) we have to make sure it remains in active mode and ii) the small signal condition. I understand part i) which requires us to look at the allowable swing of the output value. What I don't get is part ii) and here is the solution: It might be a bit blurry but the first part says v_be(max) approximately equals to 10 mV. Here v_be is voltage across the be junction due to the small signal I think?