Didn't read the linked paper. But the dynamic resistance (either \$r_e^{\:'}\$ or \$r_\pi\$) can be applied either at the emitter or the base. They both reflect the tangent slope at the quiescent point found on the non-linear the Shockley diode equation curve. Since the active mode base current is \$\beta+1\$ (or \$\approx \beta\$) different from the emitter current the slope is altered by that difference. You just don't get to do both viewpoints at once. You pick one for a purpose at hand.
↧