EE121B Homework #5 (Spring 2010)
1. In class we set up the Poisson's equation for a MOSCAP
d 2 ( x)
=
si
dx2
=
q
si
=
q
si
+
( N D n + p)
q ( x )
q ( x)
N D exp
+ ND
kT
kT
N D exp
with ()=0.
we can actually integrate this once by noticing
EE121B Spring 2010 HW#3
1.
Using the small signal circuit for BJT, show that if we ac-grounded the collector, the ac current gain
i
gm rbe
h fe = c =
.
ib 1 + j rbe ( C be + C bc )
Now put in the term for Cb'e to show that
h fe =
2.
ic
=
ib
gm rbe
qI
qI x