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1
cbi
C
bb
R
be
C
'
'
e
b
m
V
g
be
R
ex
R
+

'
'
e
b
V
cbx
C
ECE145C/218C PS 4.
Above is a device
model . Recall that
f
m
depl
be
be
g
C
C
τ
+
=
,
.
Let
us take Cje=32 fF, beta=50, Ccbi=2.2 fF,
Ccbx=6.0 fF, Rbb=38 Ohms, Rex=2.8Ohms,
and tau_f=0.28 ps.
Lets use this device model
in circuit calculations below.
The transistor,
incidentally, has Ae=0.6 um x 4.3 um emitter
area, has a peak 450 GHz ft and 490 GHz
fmax, operates at a maximum of 12 mA/um^2
at Vce=0.7 volts.
For the purpose of this problem set only, to
simplify the calculations, let us move all the
collectorbase capacitance inside Rbb, eg
change Ccbi to 8.2 fF, and set Ccbx to 0 fF
More details though not needed for this problem set regarding this transistor can be
found at
http://www.ece.ucsb.edu/Faculty/rodwell/Downloads/Publications/Griffith_DRC2005_digest.pdf
Ree
Rcs
Ree
RL
RL
RL
RL
Problem 1: The circuit to the left is one stage
in a string of identical differential stages. The
positive supply is zero volts and the negative
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This note was uploaded on 08/06/2008 for the course ECE 145 taught by Professor Rodwell during the Fall '07 term at UCSB.
 Fall '07
 RODWELL

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