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CMOS Transient Analysis
Experiment 7
Question 1: For both the circuit having the 100pF capacitors and the circuit having the 390pF
capacitors, calculate the average propagation delay ((
)
2
/
)
PHL
PLH
t
t
+
, and the maximum switching
frequency:
r
f
t
t
f
+
=
1
max
What effect does the increased capacitance (i.e., replacing the 100pF capacitors with the 390pF
capacitors) have on the measurements?
Performing calculations for the 100pF capacitors:
ns
t
ns
ns
t
t
t
APD
PHL
PLH
APD
96
2
)
0
.
100
0
.
92
(
2
)
(
=
⇒
+
=
+
=
For
out
V
,
MHz
f
ns
ns
t
t
f
r
f
139
.
5
)
0
.
95
0
.
93
(
1
)
(
1
max
max
=
⇒
+
=
+
=
For
in
V
,
MHz
f
ns
ns
t
t
f
r
f
291
.
5
)
100
89
(
1
)
(
1
max
max
=
⇒
+
=
+
=
Performing calculations for the 390pF capacitors (
out
V
):
ns
t
ns
ns
t
t
t
APD
PHL
PLH
APD
258
2
)
274
242
(
2
)
(
=
⇒
+
=
+
=
MHz
f
ns
ns
t
t
f
r
f
5174
.
1
)
344
315
(
1
)
(
1
max
max
=
⇒
+
=
+
=
As seen by the difference in the values of the
APD
t
increased when the capacitors were replaced
from 100pF to 390pF, respectively, physically agreeing because the
Question 2: (Part a): Derive a differential equation for
in
V
by applying KCL. Recall that KCL
involves summing the currents entering and leaving a given node. Since
in
V
is the only node of
unknown voltage you need to define the currents going through the capacitors and resistor as
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 Spring '08
 Zhang
 Frequency

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