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Solutions
Solutions for CMOS VLSI Design 4th Edition. Last updated 12 May 2010.
Chapter 1
1.1 Starting with 100,000,000 transistors in 2004 and doubling every 26 months for 12
⎛----------------⎞
years gives 10 • 2 ≈ 4.6B transistors.
1.3 Let your imagination soar! 1.5
A B C
D
Y
1.7
A
Y (a) A Y (b) B
A A Y B
(c) B C Y
(d)
1
2 SOLUTIONS
1.9
A1A1A0A0
Y0
Y1
A0
A1
Y0 A2
Y2
A1
Y3
Y1 A0
(a) (b)
1.11 The minimum area is 5 tracks by 5 tracks (40 λ x 40 λ = 1600 λ2). 1.13
B A
GND Y VDD
n+ n+ n+ p+ p+ p substrate n well
1.15 This latch is nearly identical save that the inverter and transmission gate feedback
CHAPTER 2 SOLUTIONS 3
has been replaced by a tristate feedaback gate.
CLK
D Y
CLK
CLK
CLK
1.17
VDD
A B C D
A D
B C F
F C D
A B
GND (a) (b)
(c) 5 x 6 tracks = 40 λ x 48 λ = 1920 λ2. (with a bit of care) (d-e) The layout should be similar to the stick diagram.
1.19 20 transistors, vs. 10 in 1.16(a).
A B
A C
B C
Y
1.21 The Electric lab solutions are available to instructors on the web. The Cadence labs include walking you through the steps.
Chapter 2
4 SOLUTIONS
2.1
W ⎛3.9•8.85⋅10−14 ⎞⎛W ⎞ W 2 ox L ⎝ 100⋅10−8 ⎠⎝ L ⎠ L
2.5 Vgs = 5 2
1.5 Vgs = 4
1
Vgs = 3
0.5
00 1 2
Vgs = 2 Vgs = 1
3 4 5
Vds
2.3 The body effect does not change (a) because Vsb = 0. The body effect raises the threshold of the top transistor in (b) because Vsb > 0. This lowers the current through the series transistors, so IDS1 > IDS2.
2.5 The minimum size diffusion contact is 4 x 5 λ, or 1.2 x 1.5 μm. The area is 1.8 μm2 and perimeter is 5.4 μm. Hence the total capacitance is
Cdb(0V) = (1.8)(0.42) + (5.4)(0.33) = 2.54fF
At a drain voltage of VDD, the capacitance reduces to
Cdb(5V) = (1.8)(0.42)⎛1 + ----------⎞–0.44 + (5.4)(0.33)⎛1 + ----------⎞–0.12 = 1.78fF
2.7 The new threshold voltage is found as
17
φs = 2(0.026)ln1.45•1010 = 0.85V
γ = 3.9•8.85•10−14 2(1.6•10−19 )(11.7•8.85•10−14 )(2•1017 )= 0.75V1/2 V = 0.7+γ φs +4 − φs =1.66V
The threshold increases by 0.96 V.
CHAPTER 3 SOLUTIONS 5
2.9 The threshold is increased by applying a negative body voltage so Vsb > 0. 2.11 The nMOS will be OFF and will see Vds = VDD, so its leakage is
−V
Ileak = Idsn = βvTe1.8envT = 69pA
2.13 Assume VDD = 1.8 V. For a single transistor with n = 1.4,
−Vt +ηVDD
Ileak = Idsn = βvTe1.8e nvT = 499pA
For two transistors in series, the intermediate voltage x and leakage current are found as:
−Vt +ηx −x η(VDD −x)−V −x
2 1.8 nvT vT 2 1.8 nvT leak T ⎝ ⎠ T
−Vt +ηx −x η(VDD −x)−V −x
e nvT ⎜1−evT ⎟ = e nvT ⎝ ⎠
x = 69 mV; Ileak = 69 pA
In summary, accounting for DIBL leads to more overall leakage in both cases. However, the leakage through series transistors is much less than half of that through a single transistor because the bottom transistor sees a small Vds and much less DIBL. This is called the stack effect.
For n = 1.0, the leakage currents through a single transistor and pair of transistors are 13.5 pA and 0.9 pA, respectively.
2.15 VIL = 0.3; VIH = 1.05; VOL = 0.15; VOH = 1.2; NMH = 0.15; NML = 0.15
2.17 Either take the grungy derivative for the unity gain point or solve numerically for VIL = 0.46 V, VIH = 0.54 V, VOL = 0.04 V, VOH = 0.96 V, NMH = NML = 0.42 V.
2.19 Take derivatives or solve numerically for the unity gain points: VIL = 0.43 V, VIH = 0.50 V, VOL = 0.04 V, VOH = 0.97 V, NMH = 0.39, NML = 0.47 V.
2.21 (a) 0; (b) 0.6; (c) 0.8; (d) 0.8
Chapter 3
3.1 First, the cost per wafer for each step and scan. 248nm – number of wafers for four
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