where E F is the Fermi level, E C is the minimum energy of the conduction band, and N C is a concentration coefficient that depends on temperature. The above relationship for n e can be shown to apply for any conduction band shape (including non-parabolic, asymmetric bands), provided the doping is weak (E C − E F ≫ kT); this is a consequence of Fermi–Dirac statistics limiting towards Maxwell–Boltzmann statistics.