With the E-MOSFET, VGS has to be, 'greater than VGS(th) to get
any drain current at all. Therefore, when E-MOSFETs are biased,
self-bias, current-source bias, and zero bias cannot be used
because these forms of bias depend on the depletion mode of
operation. This leaves gate bias, voltage-divider bias, and source
bias as the means for biasing E-MOSFETs.