ELECTRONICS(I):Test #1
12’ Spring 04/06/12
As per the course syllabus, this test constitutes 28% of your course grade. Show all your work. No
credit will be given to unsupported answers. Arrange solutions in the order in which the problems
appear in the test. Box your answers.
Problem 1: A simple circuit is configured using a voltage amplifier and other circuit components. A
series of measurements are performed, each with a different condition, in order to extract the
three model parameters of the voltage amplifier, Ri , Ro , and Avo .
i) Measurement One: Condition: RX  0
5
4
3
2
1
0
-1
-2
-3
-4
-5
Amp
vS (t )
RX
RY
vS (t )
Time [s]
ii) Measurement Two: Condition: RX  0
5
4
3
2
1
0
-1
-2
-3
-4
-5
RY  12 k
RX
RY
vS (t )
Time [s]
iii) Measurement Three: Condition: RX  12 k 
5
4
3
2
1
0
-1
-2
-3
-4
-5
Time [s]
5
4
3
 2
1
vO(t) 0
-1
-2
 -3
-4
-5
vO (t )
Time [s]
RY  12 k
Amp
vS (t )
vO (t )
RY   k
Amp
vS (t )
5
4
3
 2
1
vO(t) 0
-1
-2
 -3
-4
-5
RX
RY
vS (t )
Time [s]
5
4
3
 2
1
vO(t) 0
-1
-2
 -3
-4
-5
vO (t )
Time [s]
1) Sketch the circuit model for the amplifier. Show the values for Ri , Ro , and Avo . (9 pts)
2) The two voltage amplifiers are connected in series to form a new voltage amplifier. Sketch the
circuit model for the new voltage amplifier. Show the values for Ri , Ro , and Avo . (6 pts)
Amp
Amp
Problem 2: Explain, describe, or illustrate the following pairs of the semiconductor terminologies in a
comparative manner. (15 pts)
i) Thermal ionization vs. Recombination
ii) n-type semiconductor vs. p-type semiconductor
iii) Diffusion current vs. Drift current
iv) Depletion capacitance vs. Diffusion capacitance
v) Zener breakdown vs. Avalanche breakdown
Problem 3. Consider a nonlinear device whose terminal circuit equation and the i  v curve are
given below.
200
i  1.3 103 (v  2.5)2
180
160
Current [mA]
140
120
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Voltage [V]
The following three circuits are built using the nonlinear device along with other linear circuit
components.
50  F
80 Ω

0.02sin 50t
v D (t )
8V



Circuit A
RX
80 Ω
iD (t)
2sin 50t
8V
vO ( t )
80
iD (t)

v D (t )
v D (t )
8V

Circuit B


Circuit C
1) For Circuit A, find the expressions for v D (t ) and vO (t ) . (8 pts)
2) For Circuit B, find the range of | v D | and | iD | . Arrange your answer in the form of
(
)  | vD |  (
) and (
)  | iD |  (
) . Show your work. (6pts)
3) For Circuit C, assume that 40   RX  200  and repeat 2). (6 pts)
Problem 4.
Consider a nonlinear device whose terminal circuit equation is given by
4 2v
i  10 (e  2v  0.2) . The following two circuits are configured using the nonlinear device and
other linear circuit components.
50  F
50  F
iM (t )


iO (t )
0.02sin 50t
50 
50 
104 (e4 +4+0.2) A
vM (t )
vO (t )
0.02 sin 50t
2V


Circuit B
Circuit A
1) For Circuit A, find the expression for i M (t ) and iO (t ) . (7 pts)
2) For Circuit B, find the expression for v M (t ) and vO (t ) . (8 pts)
Problem 5. Consider the following circuit and answer the questions. Assume diodes are ideal.
2:1
30sint

500  F
200 Ω
vM (t )
Circuit A

200 Ω

vO (t )

1) Sketch the general shape of v M (t ) . Assume Vr  2 V for the ripple in v M (t ) . (5 pts)
Now assume you have the following six Zener diodes as described below
i) Three 2 V Zener diodes with VZ  2 V , rz  20  , and I ZK  10 mA .
ii) Two 3 V Zener diodes with VZ  3 V , rz  40  , and I ZK  10 mA .
iii) One 6 V Zener diode with VZ  6 V , rz  50  , and I ZK  3mA .
2) Use your Zener diode(s) to build Circuit A which produces a 5 V dc for vO (t ) with minimal ripple
component. Also, specify the peak-to-peak value of the ripple, vO (t ) peak  peak . Justify your
design. (8 pts)
3) Repeat 2) to produce a 6 V dc for vO (t ) with minimal ripple component in the output voltage.
Specify vO (t ) peak  peak . Justify your design. (7 pts)
Problem 6. In the circuit shown below, assume all the circuit components are ideal.
7.5 V
vS (t )
7.5 V

vS (t )

1: 2
 vR (t )

vS (t )

50μF

100Ω
vM (t )



VZ =15 V
VZ =15 V
vO (t )

Referring to the given vS (t ) waveform, sketch the waveforms for vS (t ) , vM (t ) , vO (t ) , and
vR (t ) . Show the maximum and minimum values on your sketch. (15 pts)
Answer Sheet for Problem 3
Name:
Student ID:
1)
2)
200
180
160
Current [mA]
140
120
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Voltage [V]
3)
200
180
160
Current [mA]
140
120
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Voltage [V]