Assignment

EE 330
Homework 6
Fall 2014
Solve problems {1 or 2} and {3 or 4} and {5 or 6}, ….and {25 or 26}. Unless specified
to the contrary, assume all n-channel MOS transistors have model parameters μnCOX =
100μA/V2 and VTn = 1V, all p-channel transistors have model parameters μpCOX =
33μA/V2 and VTp= -1V. Correspondingly, assume all npn BJT transistors have model
parameters JS= 10-14A/μ2 and β=100 and all pnp BJT transistors have model parameters
JS= 10-14A/μ2 and β = 25. If the emitter area of a transistor is not given, assume it is
100μ2 . If parameters are needed for process characterization beyond what is given, use
the measured parameters from the ON 0.5μ process given below as model parameters.
Problem 1
Size an n-channel transistor in the AMI 0.5u CMOS process so that the
impedance in the switch-level model is 4000Ω when operating with a 3.5V power supply.
Repeat for an n-channel transistor in the IBM 0.13u CMOS process when operating with
a 1.5V supply.
Problem 2
If a minimum-sized inverter designed in the AMI 0.5u CMOS process
could directly drive a minimum-sized inverter designed in the IBM 0.13u CMOS process,
what would be tHL and tLH? Assume a supply voltage of 1.5V. Neglect any interconnect
parasitics.
Problem 3
Using the short-channel α-law model, determine the impedance in the
switch-level model of the MOSFET for a square (W=L) n-channel device if the shortchannel device has the same μCOX and VT as in the IBM 0.13μ process but with shortchannel parameters θ1=θ2=1/2 and α=1.25. Comment on how the short-channel effect
changes the switching performance of the MOSFET.
Problem 4
Consider the following circuit
a)
Obtain the voltage VOUT if VIN=-4V.
b)
Obtain the current through R2 if VIN=8V
c)
Obtain an expression for and plot VOUT for one period of the input if
VIN = 12sin1000t
2K
VOUT
R1
VIN
D1
R2
1K
Page 1 of 12
Problem 5
Assume the junction area of D1 is 100μ2 and that of D2 is 9 times as large.
Determine the current ID1 if VX=1.5V. Assume JS for the process where the diodes are
fabricated is 5fA/μ2.
1K
ID1
VX
D1
ID2
D2
Problem 6
Analytically determine the variable indicated by a ? in the following
circuits. Assume the devices are in a process with VTN=1V, and μnCOX=100μAV-2
5V
5V
5K
M1
20K
VOUT=?
M1
W=6u
L=2u
3V
VOUT=?
W=12u
L=1.5u
2V
Page 2 of 12
Problem 7
Analytically determine the variable indicated by a ? in the following
circuits. Assume the devices are in a process with VTN=1V, VTP=-1V, μnCOX=100μAV-2
and μpCOX=33μAV-2
6V
M2
10V
W=4u
L=4u
W=4u
L=2u
M1
M2
VOUT=?
M1
W=12u
L=4u
IOUT=?
W=6u
L=2u
R2
I1
1K
400μA
Problem 8
Consider the following circuit.
a) If VIN=3V, determine the dimensions of M1 that will result in an output voltage
of 3V. Assume that the dimensions of M2 are W2=10u and L2=2u. The relevant
model parameters of the devices are VTN=1V, VTP=-1V, μnCOX=100μAV-2
and μpCOX=33μAV-2 .
b) Repeat part a) if the goal is to have an output voltage of 0.5V.
5V
M2
VOUT
VIN
M1
Page 3 of 12
Problem 9
Determine the currents indicated with a ? in the following circuits.
Assume the diodes are ideal.
2K
10V
2K
15V
I1=?
I2=?
2K
2K
15V
9V
Problem 10
Determine the currents indicated with a ? in the following circuits.
Assume the diodes are ideal.
2K
2K
2K
20V
2K
I1=?
20V
I2=?
4K
4K
7V
30V
Problem 11 Assume the op amp is ideal and biased with VDD=20Vand VSS=-20V and
2
the diode is characterized by model parameters: JSX=0.5A/μ , VG0=1.17V, m=2.3.
Assume the area of the junction is 300u2.
a) Determine VOUT if T= -20oC
b) Repeat part a) if T= 40oC.
c) Repeat part a) if T=120oC
10K
VOUT
0.575V
Page 4 of 12
Problem 12
Determine VOUT for the following circuit. Assume the devices M1 and
M2 are identically sizes with W=L=5u. . The relevant model parameters of the devices
are VTN=1V, VTP=-1V, μnCOX=100μAV-2 and μpCOX=33μAV-2 .
5V
3V
M1
VOUT
M2
Problem 13
Determine the output voltage for the following circuits
8V
8V
6K
3K
600K
VOUT
400K
VOUT
AE=500μ2
AE=200μ2
Problem 14
Determine the currents labeled with a ?
8V
8V
W=10μ
L=2μ
I=?
M2
W=15μ
L=4μ
I=?
AE=100μ2
M1
Page 5 of 12
W=40μ
L=2μ
Problem 15 Design a circuit using only MOS transistors that has an output voltage of
3V. In addition to the transistors, you have a single dc power supply of 10V available.
You may use as many MOS transistors as you want and can specify any size for the
devices.
Problem 16
only BJTs.
Repeat Problem 15 if instead of using MOS transistors, you have available
Problem 17 Assume a junction capacitor has a capacitance of 500fF with zero volts
bias. What will be the value of this capacitor with a reverse bias of 3V? With a forward
bias of 250mV?
Problem 18 Design a voltage programmable capacitor that varies between 2pF at 0V
bias and 2.5pf at a bias of 4V.
Problem 19 Sketch a cross-sectional view along the BB’ cross-section for the CMOS
layout shown below. Assume a basic CMOS process in which the n-select mask is
generated from the compliment of the p-select mask.
Problem 20
C
Repeat Problem 19 along the CC’ cross-section
D
A
A’
B’
B
Layer Map :
C’
D’
Page 6 of 12
Active
n-well
Poly 1
Metal
Contact
p-select
Poly 2
Problem 21 Assume the emitter area for the BJT is 400μ2, the base area is 800 μ2 ,
β=100, and JS=50fA/μ2. Determine the output voltage VOUT for the two circuits shown if
A=0V.
12V
400K
12V
1.5K
VOUT
400K
1.5K
VOUT
200uF
Asin(1000t)
Problem 22 The process parameter β for a BJT is quite variable from one process run
to another. If the β in a process varies between 85 and 125, what is the corresponding
variation in the output voltage VOUT for the circuit shown?
12V
400K
1.5K
VOUT
R1
Problem 23 The 400K resistor in the previous problem is often termed a biasing
resistor since it is used to establish the desired value of the quiescent output voltage and
the biasing scheme whereby this single resistor is used to establish the base current is
termed a self-bias. An alternative biasing scheme is shown below. In this circuit, the
resistor R1 has been reduced to 40K and a second resistor R2 has been added to the
circuit. This scheme is often termed a fixed-bias scheme. In this circuit, determine R2
so that the quiescent output voltage is the same as that for the circuit of Problem 9 when
the value of β is the nominal value of 100.
12V
R1
40K
1.5K
VOUT
R2
R3
0.5K
Page 7 of 12
Problem 24 Using the value of R2 determined in the previous problem, compare the
variation of the output voltage of the self-bias circuit to that of the fixed-bias circuit if
β varies between 85 and 125
.
Problem 25 (weighted as two problems) Using Verilog, build a counter that outputs to
a seven segment display. Whenever the INPUT makes a low to high transition, the
counter should increase by one. This should be reflected by the seven segment display.
Each bit of the seven segment display is controlled by an individual output. A high output
corresponds to a lit segment while a low output causes an unlit segment. The counter
should go back to zero upon passing 9. Label your outputs clearly and prove your design
with sufficient testing.
Problem 26 (weighted as two problems) Using Verilog, build a 3-8 bit decoder. For an
input of 000 to 111 it should decode into an 8-bit number with ones from position 0 to the
position noted by the decimal equivalent of the 3-bit binary number. For example, 011
will correspond to 00001111 and 100 corresponds to 00011111. Your design should be
verified with a computer simulation.
Problem 27 (Extra credit) Using Verilog, build a two-digit counter that goes back to zero
after passing 99.
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Page 9 of 12
AMI 0.5u Process Description
Continued
Page 10 of 12
Page 11 of 12
IIBM 0.13u Process Description Continued
Page 12 of 12

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