Where NA is the doping concentration of the p-type substrate, and e is the permittivity of silicon (1.04 x 10-12 F/cm) The parameter y has the dimension of √V and is typically 0.5 V1/2 ,Finally , note that Eq. (5.30) applies equally well for p-chaael devices with VSB replaced by the reverse bias of the sub, VBS (alternatively Replace VSB by [VSB] for both devices).