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ECE 3355 – Final Exam
December 12, 2015
Keep this exam closed until you
are told to begin.
1. This exam is closed book, closed notes. You may use one 8.5” x 11”
crib sheet, or its equivalent.
2. Show all work on these pages. Show all work necessary to complete
the problem. A solution without the appropriate work shown will receive no
credit. A solution that is not given in a reasonable order will lose credit.
Clearly indicate your answer (for example by enclosing it in a box). If your
answer is a plot, no box is needed.
3. It is assumed that your work will begin on the same page as the
problem statement. If you choose to begin your work on another page, you
must indicate this on the page with the problem statement, with a clear
indication of where the work can be found. If your work continues on to
another page, indicate clearly where your work can be found. Failure
to indicate this clearly will result in a loss of credit.
4. Show all units in solutions, intermediate results, and figures. Units in
the exam will be included between square brackets.
5. Do not use red ink. Do not use red pencil.
6. You will have 170 minutes to work on this exam.
1. ________________/20
2. ________________/45
3. ________________/45
4. ________________/45
5. ________________/45
Total = 200
ECE 3355 Final Exam – December 12, 2015 – Page 2
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 3
1. {20 Points} Use the circuit below to solve this problem. Assume ideal op
amps, assume that all resistors have resistance of 1[k], and assume that vI = 1[V].
Find vO.
R
R
R
R
R
R
R
+15[V]
R
+15[V]
vI
+
R
-
-
-
+
-15[V]
-15[V]
+30[V]
+15[V]
R
-15[V]
vO
+
+
R
-30[V]
R
ECE 3355 Final Exam – December 12, 2015 – Page 4
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 5
2. {45 Points} Use the circuit below to solve this problem. Assume an ideal op
amp.
a) Find the voltage gain VA / VIN.
b) Find the voltage gain Va / Vin as a function of angular frequency.
c) Find the voltage gain va / vin as a function of time, if
vIN(t) = 6[V] + 3[V]cos(300[rad/s]t).
+
4.7[k]
+
vIN(t)
-
2.2[k]
1[k]
-
+
LX =
8.2[mH]
vA +
2.2[k]
ECE 3355 Final Exam – December 12, 2015 – Page 6
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 7
3. {45 Points} Assume an ideal op amp in the schematic in Figure 1. Find the
values of R2, CX, and LX that will produce the magnitude Bode plot that has the
straight-line approximation given in the plot in Figure 2.
CX
R2
R1 =
1[k]
LX
-
vIN
vOUT
+
Figure 1
│H(f)│, in [dB]
35
15
-5
f, [Hz]
0.1
1
10
100
1000
Figure 2
104
105
ECE 3355 Final Exam – December 12, 2015 – Page 8
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 9
4. {45 Points} The characteristic curve for the device, called a karrleeloid, is
shown in Figure 1. The device schematic symbol is shown in Figure 2. The
device is placed in the circuit in Figure 3.
a) Find a model for each of the four regions of this device.
b) Find a test that could be used to determine whether the correct region had
been chosen in a guess and test analysis process. There should be one test
given for each region.
c) Find the solution or solutions, if any, for iB in the circuit in Figure 3.
iCL, [mA]
24
19
14
12
10
6
2
3
4
vCL, [V]
-8
-6
-5
-4
-2
6
8
Figure 1
1.2[k]
+
1.14[k]
-
+
vCL
iCL
iB
3.3[k]
1.5[k]
Figure 2
27[V]
50iB
Figure 3
ECE 3355 Final Exam – December 12, 2015 – Page 10
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 11
Room for extra work
ECE 3355 Final Exam – December 12, 2015 – Page 12
5. {45 Points} Use the circuit shown to solve this problem. Assume that for the
transistor,  = 50, and that it is operating at room temperature.
a) Assume for part a) that the transistor is biased into the linear region, with
r = 300[]. Find the voltage gain vo /vi in the passband, if RC = 3.3[k].
b) Assume for part b) that the transistor is biased into the linear region, with
r = 300[]. Find the voltage gain vo /vi in the passband, as a function of RC.
c) Find the range of values for RC that will have the transistor biased into the
linear region.
+15[V]
+15[V]
RE =
1.5[k]
R1 =
2.2[k]
C1 = 2.2[mF]
Q1
+
vi
-
vo
R2 =
6.8[k]
RC
-15[V]
-15[V]
ECE 3355 Final Exam – December 12, 2015 – Page 13
1. {20 Points} Use the circuit below to solve this problem. Assume ideal op
amps, assume that all resistors have resistance of 1[k], and assume that vI = 1[V].
Find vO.
ECE 3355 Final Exam – December 12, 2015 – Page 14
ECE 3355 Final Exam – December 12, 2015 – Page 15
2. {45 Points} Use the circuit below to solve this problem. Assume an ideal op
amp.
a) Find the voltage gain VA / VIN.
b) Find the voltage gain Va / Vin as a function of angular frequency.
c) Find the voltage gain va / vin as a function of time, if
vIN(t) = 6[V] + 3[V]cos(300[rad/s]t).
ECE 3355 Final Exam – December 12, 2015 – Page 16
ECE 3355 Final Exam – December 12, 2015 – Page 17
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4. {45 Points} The characteristic curve for the device, called a karrleeloid, is
shown in Figure 1. The device schematic symbol is shown in Figure 2. The
device is placed in the circuit in Figure 3.
a) Find a model for each of the four regions of this device.
b) Find a test that could be used to determine whether the correct region had
been chosen in a guess and test analysis process. There should be one test
given for each region.
c) Find the solution or solutions, if any, for iB in the circuit in Figure 3.
ECE 3355 Final Exam – December 12, 2015 – Page 22
ECE 3355 Final Exam – December 12, 2015 – Page 23
ECE 3355 Final Exam – December 12, 2015 – Page 24
ECE 3355 Final Exam – December 12, 2015 – Page 25
5. {45 Points} Use the circuit shown to solve this problem. Assume that for the
transistor,  = 50, and that it is operating at room temperature.
a) Assume for part a) that the transistor is biased into the linear region, with
r = 300[]. Find the voltage gain vo /vi in the passband, if RC = 3.3[k].
b) Assume for part b) that the transistor is biased into the linear region, with
r = 300[]. Find the voltage gain vo /vi in the passband, as a function of RC.
c) Find the range of values for RC that will have the transistor biased into the
linear region.
ECE 3355 Final Exam – December 12, 2015 – Page 26
ECE 3355 Final Exam – December 12, 2015 – Page 27