An N-channel MOSFET with n+ poly-Si gate is fabricated on a 15 Q-cm p-type Si wafer with oxide fixed charge density of QF=q 8 x 100 cm (q is the elementary charge), Z = 50 m, L=2 m, xo 5 nm, = 750 cm/V-sec. Use the square law theory where needed. (a) Calculate the flat-band voltage, VFB. (b) Calculate the threshold voltage, VT. (c) Calculate the saturation drain current, IDsat, and the transconductance, gm, for VGS= 2 V and VDS = 3 V. (d) Calculate the cut-off frequency fmax for VGs- 2 V and VDS= 2 V. (e) Calculate (a) through (c) for L = 0.5 m. (f) You are asked to change the threshold voltage of this N-MOSFET to VT=0.5 V, but you are not allowed to change the oxide thickness. Explain what you need to do and give a quantitative answer which parameter of the MOSFET structure and by what amount should be changed.