UNIVERSITY OF CALIFORNIACollege of EngineeringDepartment of Electrical Engineering and Computer SciencesEE 130 Discussion Section 101Spring 2007 Frank LiaoWorksheet 6A(Adapted from EE130 2003 and 2004)1) Suppose an NMOSFET has a VT of 0.5V. Sketch a band diagram for this MOSFET along slice Q-Q’ (shown below) for VDS = 1.0V and VGS = 1.0V. Also sketch a band diagram for the same device along the W-W’ slice. Assume that Q-Q’ is the drain side.2) Suppose we increase the channel doping of this MOSFET. Assume I change the gate workfunction so that the threshold voltage stays unchanged.a) What would be the impact on the output resistance? Give reasons.Output resistance should generally increase, since I would reduce the penetration of drain-side depletion region into the channel.W-W’Q-Q’b) When I changed the gate workfunction – should I have increased it or decreased it tokeep the VT constant?The gate workfunction should be decreases, resulting in a reduction in VFB and therefore in VT, to compensate for the increase in VT due to increased doping.3) Suppose I increase the L of the MOSFET, how will the small-signal output resistance change? Why?The MOSFET should have a higher small-signal output resistance, since it will suffer lessfrom channel length modulation effects.4) Assume the MOSFET has a series resistance that is approximately 25% of the large signal channel resistance (IDsat/VDS). Draw a band diagram for the MOSFET along slice X-Y for the MOSFET, assuming VT = 0.5V, VG = 1V, and VD = 1V. Make sure you include the source/drain regions in your band diagram.5) For this MOSFET, indicate how Vdsat and Idsat change (increase (↑) or decrease (↓) or unchanged (n/c)) when various device parameters are changed as
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