10/15/10
Name_________________ UK ID______________
EE 461G Mid-Term Exam
Print your name. You must show your work to receive partial credit. You may bring a piece of
paper with formula, a calculator, a ruler, a pencil, and an eraser.
Problem 1 (30 points) Schematically draw transfer characteristics of circuits (a) and (b)
separately and their output voltage in the space below. Point out which one is a rectifier and
which one is a clipping circuit? (The diodes are ideal diodes with Vf=0.7V)
R=2 k
+
D1
+
+
vIN
D1
vout
+
vIN
vout
R=10 k
D2
–
–
–
–
(a)
(b)
Vout (V)
Vout
2
VIN
1
1
VIN
2
3
4
5
6
t (ms)
-1
-2
Transfer characteristics for (a)
Vout for (a)
Vout (V)
Vout
2
VIN
1
1
VIN
2
3
4
5
6
t (ms)
-1
-2
Transfer characteristics for (b)
Vout for (b)
1
Problem 2 (35 points) Considering the following circuits: (a) Derive the equations for transfer
characteristics using the piecewise linear model (both diodes are the same with rd=0.5 k and
Vf=0.7V); (b) Draw the transfer characteristics; (c) Draw the output voltage curves Vout in the
graph below.
1 k
+
vin
V2=3V
D1
~
vout
D2
V1=3V
–
Vout (V)
10
VIN
5
0
1
2
3
4
5
6
7
8
9
10
11
t (ms)
-5
-10
2
Problem 3 (35 points) A bridge power supply circuit is shown below. Assuming the turn-on
voltage of all diodes is Vf=0.7V. The input is vin= 10Sin(2ft) where f=1kHz. In the circuit,
C=20F and R1=0.2k. For the Zener diode (Z1), Vf=0.7V and Vzk=5V.
(a) Calculate the ripple voltage on the capacitor for Vin at the peak.
(b) Draw the curves of vc vs. t and vout vs. t together with the curve of vin vs. t
(c) If the load current (IL) varying from 5 mA to 10 mA, what are the maximum and minimum
powers on the Zener diode (Z1)?
+
D4
D1
R1
I1
vin
IL
+
vout
I2
D3
–
D2
vc
C
Z1
Load
–
3