ECE 403 Homework 6, due at 10:40 am on Friday, 2/27/09 1) Capture the circuit, with W/L=40 μ /1.6μ for M1 and M2 as shown, and with model vto=.7, kp=100u, lambda=.05, gamma=.5, phi=.7 for n-channel FETs, so that simulations will include 2 nd order effects. a) Use PSpice to simulate a DC sweep of Iin from 0 to 200 μ A, then use “Add trace” from the “Trace” menu of Probe to plot Id(m1) and Id(m2) on the same plot. b) Explain why Id(m1) and Id(m2) are approximately equal for small Iin, but diverge for larger Iin. c) Neglecting 2 nd order effects, show that for Iin=100uA, M2 is active for Rx<47k Ω , approximately. d) Repeat the previous DC sweep with this new value of Rx and repeat the Probe plot for Id1 and Id2. In that same Probe window, select “Plot” from the menu bar, then “Add plot to window” from the pull down menu. On the resulting new plot, add the traces for vd(m1) and vd(m2). Explain what happens to id(m1) and id(m2) in the first plot when vd(m1) and vd(m2) cross in the 2 nd plot.
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- Spring '08
- Approximation, Early effect, Cascode Current Mirror