Question: Starting from the expression for the MOSFET unity-gain frequency, fT=gm/2*pi*(Cgs+Cgd) and making the approximation that Cgs>>Cgd and that the overlap component of Cgs is negligibly
Starting from the expression for the MOSFET unity-gain frequency, fT=gm/2*pi*(Cgs+Cgd) and making the approximation that Cgs>>Cgd and that the overlap component of Cgs is negligibly small, show that for an n-channel device fT=3*un*Vov/4*pi*L^2 Observe that for a given channel length, fT can be increased by operating the MOSFET at a higher overdrive voltage. Evaluate fT for devices with L=1.0 um operated at overdrive voltages of 0.25 V and 0.5 V. Use un=450 cm^2/Vs.
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