We have the symbols for depletion mode and enhancement mode MOSFETs - notice the dashed versus solid lines.
In a depletion mode MOSFET gate voltage closes off the conductive channel from source (S) to drain (D).
With an enhancement mode MOSFETs gate voltage opens the conductive channel from source to drain.
by Robert Keim
In Partnership with Dove Electronics
by Luke James
by Gary Elinoff