
1242 Part 3 Digital Electronics
16.35 Consider the series of CMOS inverters in Figure P16.35. The threshold volt-
ages of the n-channel transistors are
V
TN
= 0.8V
, and the thresh-
old voltages of the p-channel transistors are
V
TP
=−0.8
V. The conduction
parameters are all equal. (a) Determine the range of
v
O1
for which both
N
1
and
P
1
are biased in the saturation region. (b) If
v
O2
= 0.6V
, determine the
values of
v
O3
,
v
O1
, and
v
I
.
16.36 (a) A CMOS inverter is biased at
V
DD
= 2.5
V. The transistor parameters
are
K
n
= K
p
= 120μ
A/V
2
,
V
TN
= 0.4
V, and
V
TP
=−0.4
V. Calculate
and plot the current in the transistors as a function of the input voltage for
0 ≤ v
I
≤ 2.5
V. (b) Repeat part (a) for
V
DD
= 1.8
V and
0 ≤ v
I
≤ 1.8
V.
16.37 The transistor parameters in the CMOS inverter are
V
TN
= 0.35
V,
V
TP
=−0.35
V,
k
n
= 80 μ
A/V
2
, and
k
p
= 40 μ
A/V
2
. Let
V
DD
= 1.8
V. (a)
Determine the peak current in the inverter during a switching cycle for
(W/L)
n
= 2
and
(W/L)
p
= 4
. (b) Repeat part (a) for
(W/L)
n
= 2
and
(W/L)
p
= 6
. (c) Repeat part (a) for
(W/L)
n
= (W/L)
p
= 4
.
16.38 A CMOS inverter is biased at
V
DD
= 3.3V
. The transistor threshold voltages
are
V
TN
=+0.4V
and
V
TP
=−0.4
V. Determine the peak current in the in-
verter and the input voltage at which it occurs for (a)
(W/L)
n
= 3
,
(W/L)
p
=
7.5
; (b)
(W/L)
n
= (W/L)
p
= 4
; (c)
(W/L)
n
= 3
,
(W/L)
p
= 12
.
16.39 A load capacitor of 0.2 pF is connected to the output of a CMOS inverter.
Determine the power dissipated in the CMOS inverter for a switching
frequency of 10 MHz, for inverter parameters described in (a) Problem
16.36 and (b) Problem 16.37.
16.40 (a) A CMOS digital logic circuit contains the equivalent of 4 million CMOS
inverters and is biased at
V
DD
= 1.8
V. The equivalent load capacitance of
each inverter is 0.12 pF and each inverter is switching at 150 MHz. Deter-
mine the total average power dissipated in the circuit. (b) If the switching
frequency is doubled, but the total power dissipation is to remain the same
with the same load capacitance, determine the required bias voltage.
16.41 A particular IC chip can dissipate 3 W and contains 10 million CMOS
inverters. Each inverter is being switched at a frequency
f
. (a) Determine the
average power that each inverter can dissipate without exceeding the total
V
DD
= 5 V
v
O2
v
I
v
O1
N
1
N
2
P
1
P
2
Figure P16.34
V
DD
= 5 V
v
O3
v
I
v
O2
P
2
v
O1
N
2
P
1
N
1
P
3
N
3
Figure P16.35
16.34 Consider the CMOS inverter pair in Figure P16.34. Let
V
TN
= 0.8V
,
V
TP
=−0.8
V, and
K
n
= K
p
. (a) If
v
O1
= 0.6V
, determine
v
I
and
v
O2
.
(b) Determine the range of
v
O2
for which both
N
2
and
P
2
are biased in the
saturation region.
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