DEBRE BERHAN UNIVERSITY
COLLEGE OF ENGINEERING
DEPARTMENT OF ELECTRICAL ENGINEERING
APPLIED ELECTRONICS-I MODEL EXAM
Prepared by: 1. Alemie Assefa (Msc)
2. Daniel Tesfaye (Msc)
3. Naod Zerihun (Msc)
December 13, 2022
Debre Berhan,Ethiopia
I. Multiple Choice
1. When transistors are used in digital circuits they usually operate in the
A. active region
B. breakdown region
C. saturation and cut-off regions
D. linear region
Answer C
2. A transistor has a 𝛽𝐷𝐶 of 250 and a base current, IB, of 20 μA. The collector current, IC,
equals
A. 500 μA
B. 5 mA
C. 50 mA
D. 5A
Answer B
3. In a transistor, collector current is controlled by
A. collector voltage
B. base current
C. collector resistance
D. all of the above
Answer B
4. In an n-channel JFET, what will happen at the pinch-off voltage?
A. The value of VDS at which further increases in VDS will cause no further increase in
ID
B. The value of VGS at which further decreases in VGS will cause no further increases
in ID
C. The value of VDG at which further decreases in VDG will cause no further increases
in ID
D. The value of VDS at which further increases in VGS will cause no further increases
in ID
Answer A
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5. Testing a good diode with an ohmmeter should indicate
A. high resistance when forward or reverse biased
B. low resistance when forward or reverse biased
C. high resistance when reverse biased and low resistance when forward biased
D. high resistance when forward biased and low resistance when reverse biased
Answer C
6. Varactor diodes are commonly used
A. As voltage controlled capacitance
B. As a constant current source
C. As voltage multiplier
D. As a constant voltage source
Answer A
7. A transistor configuration with the lowest current gain
A. Common base
B. Common emitter
C. Common collector
D. Emitter follower
Answer A
8.
An extrinsic semiconductor is
A. Pure semiconductor
B. Good insulator
C. Doped semiconductor
D. Good conductor
Answer C
9. The peak inverse voltage of a half wave rectifier circuit is approximately equal to the
____of the input signal
A. Peak Amplitude
B. Frequency
C. Voltage sinusoidal
D. Current
Answer A
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10. Silicon that has been doped with a trivalent impurity is called
A. N-type semiconductor
B. P-type semiconductor
C. Intrinsic semiconductor
D. Extrinsic semiconductor
Answer B
11. In an n-type semiconductor holes are
A. Minority carriers
B. Majority carriers
C. Protons
D. Charge carriers
Answer A
12. What is the barrier potential of germanium at room temperature?
A. 0.4v
B. 0.7v
C. 0.5v
D. 0.3v
Answer D
13. What is the input control parameter of a FET?
A. Gate voltage
B. Source voltage
C. Drain Voltage
D. Gate Current
Answer A
14. The maximum reverse voltage that can be applied before current surges is called
A. Reverse recovery time
B. Maximum junction voltage
C. Forward voltage
D. Reverse break down voltage
Answer D
15. The most important application of schottky diodes is in
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A. Digital computers
B. Power supplies
C. Amplifier circuits
D. Voltage regulators
Answer A
16. When the emitter junction is forward biased while the collector junction is reverse biased
the transistor is at_______region.
A. Cut-off
B. Saturation
C. Active
D. Breakdown
Answer C
17. The average dc voltage of a full wave rectifier circuit is ____of the value of the peak
input voltage.
A. 31.8%
B. 48.1%
C. 63.6%
D. 1%
Answer C
18. The removal by electronic means of one extremity of an input waveform is called____
A. Filtering
B. Clamping
C. Amplifying
D. Clipping
Answer D
19. The peak inverse voltage (PIV) across a non-conducting diode in a bridge rectifier equals
approximately
A. Half the peak secondary voltage
B. Twice the peak secondary voltage
C. The peak value of the secondary voltage
D. Four times the peak value of the secondary voltage
Answer C
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20. What is the current through the diode?
A. 1 mA
B. 0.975 mA
C. 0.942 mA
D. 0.0 Ma
Answer A
21. A PN junction allows current flow when
A. the p-type material is more positive than the n-type material
B. the n-type material is more positive than the p-type material
C. both the n-type and p-type materials have the same potential
D. there is no potential on the n-type or p-type materials
Answer A
22. .Why is heat produced in a diode?
A. due to current passing through the diode
B. due to voltage across the diode
C. due to the power rating of the diode
D. due to the PN junction of the diode
Answer A
23. A commonly used pentavalent material is
A. Arsenic
B. Boron
C. Gallium
D. Neon
Answer A
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24. When an electron jumps from the valence shell to the conduction band, it leaves a gap.
What is this gap called?
A. Energy gap
B. Hole
C. Electron-hole pair
D. Recombination
Answer B
25. In a C-E configuration, an emitter resistor is used for
A. Stabilization
B. ac signal bypass
C. collector bias
D. higher gain
Answer A
26. The temperature coefficient of resistance of a semiconductor is
A. Positive
B. Negative
C. Zero
D. Infinity
Answer B
27. A heavily doped semiconductor has
A. High resistance
B. No effect on the semiconductor characteristics
C. More heat dissipation
D. Low resistance
Answer D
28. ___is the current gain for the common emitter configuration
A. 𝛼
B. 𝛾
C. 𝛽
D. 𝛿
Answer C
29. A MOSFET is sometimes _____FET
A. Open gate
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B. Shorted gate
C. Metallic gate
D. Insulated gate
Answer D
30. ______ is considered a current controlled device
A. Diode
B. Field effect transistor
C. Bipolar junction transistor
D. Resistor
Answer C
31. What is the principal characteristics of a zener diode?
A. A constant current under conditions of varying voltage
B. A high forward current rating
C. A constant voltage under conditions of carrying current
D. A very high PIV
Answer C
32. A method of connecting amplifiers in cascade
A. Configuration
B. Coupling
C. Link
D. Stages
Answer B
33. What is the largest region of a bipolar transistor?
A. Base
B. Emitter
C. Collector
D. P-region
Answer C
34. If the line frequency is 60Hz,the output frequency of a bridge rectifier is
A. 30Hz
B. 60Hz
C. 120Hz
D. 240Hz
Answer C
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35. Which of the following is considered a unipolar device?
A. Capacitor
B. Inductor
C. FET
D. BJT
Answer C
36. What is also called as the conventional amplifier?
A. Common collector
B. Emitter follower circuit
C. Common base circuit
D. Common emitter circuit
Answer D
37. What are the three terminals of a FET?
A. Gate, Source and Drain
B. Plate, Cathode and Battery
C. Gate ,Source and Battery
D. Base ,Emitter and collector
Answer A
38. A FET without a channel and no current occurs with zero gate voltage is
A. Enhancement mode FET
B. Depletion mode FET
C. CMOS
D. Metal oxide transistor
Answer A
39. Equivalent of transistor at saturation in JFET is _______?
A. Breakdown
B. Constant current
C. Pinch-off
D. Ohmic
Answer D
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40. JFET’s input impedance is _______
A. Approaches unity
B. Approaches zero
C. Approaches infinity
D. Is unpredictable
Answer C
41. _____is the maximum amount of reverse voltage which can be applied on a diode before
breakdown point is reached.
A. Zener Voltage
B. Peak inverse voltage
C. Breakdown voltage
D. Threshold voltage
Answer B
42. The purpose of adding an impurity atom to an intrinsic crystal is
A. To alter its insulating property
B. To increase its electric conductivity
C. To stop conduction
D. To increase the resistivity of the semiconductor material
Answer B
43. A reverse bias pn junction has __________
A. Very narrow depletion layer
B. Almost no current
C. Very low resistance
D. Large current flow
Answer B
44. In an intrinsic semiconductor, the number of free electrons ____
A. Equals the number of holes
B. Is greater than the number of holes
C. Is less than the number of holes
D. None of the above
Answer A
45. A zener diode is used as
A. an amplifier
B. a voltage regulator
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C. a rectifier
D. a multivibrator
Answer B
46. A series resistance is connected in the zener circuit to______
A. properly reverse bias the zener
B. protect the zener
C. properly forward bias the zener
D. none of the above
Answer B
47. Thermal runaway occurs when ……….
A. Collector is reverse biased
B. Transistor is not biased
C. Emitter is forward biased
D. Junction capacitance is high
Answer B
48. For faithful amplification by a transistor circuit, the value of VBE should ………. for a
silicon transistor
A. Be zero
B. Be 0.01 V
C. Not fall below 0.7 V
D. Be between 0 V and 0.1 V
Answer C
49. The average value of a half-wave rectified voltage with a peak value of 200 V is
A. 63.7 V
B. 127.2 V
C. 141 V
D. 31.85V
Answer A
50. One is not the application of a PN junction diode.
A. Wave shaping circuit
B. Amplification
C. Rectification
D. Voltage Multiplier
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Answer B
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