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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 nchannel 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
 BILBRO

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