4. si mosfet: assume the lateral electric field at the point where the inversion charge pinches off is given by esat=vds(sat)/l. (a) determine esat for l=3, 1.0, 0.50, 0.25 and 0.13 m for vds(sat) = 1 v. (b) for each case given in part (a), estimate the carrier drift velocity.