@user1390491 Just to add another note, because the gain of your amplifier depends strongly on the input signal value at any given moment, this amplifier stage also is highly distorting of larger signal inputs. \$r_e^{\:'}\$ varies with the signal. So this kind of stage almost always finds itself in larger circuits with the use of global NFB to correct the distortion. By itself the high distortion is either ignorantly ignored or isn't important due to a very small input signal, if not ignored. Rb is also usually a poor way to bias -- depends too much on the BJT.
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