جامعة اإلسكندرية كلية الهندسة قسم الهندسة الكهربية أبريل ٢٠١٥

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Alexandria University Faculty of Engineering Electrical Engineering Department April 2015 1a EE 132 Electronic Devices and Circuits First Year Time allowed: 1½ hours جامعة اإلسكندرية كلية الهندسة قسم

1 Alexandria University Faculty of Engineering Electrical Engineering Department April a EE 132 Electronic Devices and Circuits First Year Time allowed: 1½ hours جامعة اإلسكندرية كلية الهندسة قسم الهندسة الكهربية أبريل ٢٠١٥ نبائط و دوائر إلكترونية السنة األولى الزمن: ساعة و نصف اإلسم : رقم الجلوس: Model (B): Mark the correct answer : Example a O b c O d O 1) a O b O c O d O 2) a O b O c O d O 3) a O b O c O d O 4) a O b O c O d O 5) a O b O c O d O 6) a O b O c O d O 7) a O b O c O d O 8) a O b O c O d O 9) a O b O c O d O 10) a O b O c O d O 11) a O b O c O d O 12) a O b O c O d O 13) a O b O c O d O 14) a O b O c O d O 15) a O b O c O d O 16) a O b O c O d O 17) a O b O c O d O 18) a O b O c O d O 19) a O b O c O d O 20) a O b O c O d O 21) a O b O c O d O 22) a O b O c O d O 23) a O b O c O d O 24) a O b O c O d O 25) a O b O c O d O Examiners: Dr. Tawfik Namour and Dr. Bassem Mokhtar page 1/5

2 26) a O b O c O d O 27) a O b O c O d O 28) a O b O c O d O 29) a O b O c O d O 30) a O b O c O d O 31) a O b O c O d O 32) a O b O c O d O 33) a O b O c O d O 34) a O b O c O d O 35) a O b O c O d O 36) a O b O c O d O 37) a O b O c O d O 38) a O b O c O d O 39) a O b O c O d O 40) a O b O c O d O Choose the correct answer for the following questions: (each question is worth one point) 1) A voltage applied to a PN junction so that it will increase the junction barrier and offer a high resistance to current flow is called what type of bias? (a) Direct (b) Forward (c) Indirect (d) Reverse 2) The resistance of increase with rise in temperature degrees. (a) Insulators (b) Semiconductors (c) Conductors (d) Dielectrics 3) Charge carrier motion which is caused by an electric field due to an externally applied voltage is known as: (a) Thermal Motion (b) Carrier Drift (c) Carrier Diffusion (d) Random motion 4) The region in a pn junction where no free charge carriers exist is called: (a) Metal Contact (b) Conduction Band (c) Valence Band (d) Depletion Region 5) A material which has an equal number of electronhole pairs and conducting electrons is known as what type of semiconductor material? (a) Intrinsic (b) Extrinsic (c) Ntype (d) Ptype 6) The process of adding impurities to crystals is known by which of the following terms? (a) Doping (b) Charging (c) Injecting (d) Processing 7) Electronhole pairs are produced by (a) Thermal energy (b) Recombination (c) Ionization (d) Doping Examiners: Dr. Tawfik Namour and Dr. Bassem Mokhtar page 2/5

3 8) In the Ptype semiconductor, what are the majority carriers? (a) The holes (b) The electrons (c) The inactive atoms (d) The inert atoms 9) What is the purpose of the pn junction diode? (a) To amplify (b) To rectify and switch (c) To rectify and amplify (d) To charge 10) How many valence electrons does a silicon atom have? (a) 1 (b) 2 (c) 3 (d) 4 11) The diffused impurities with valence electrons are called donor atoms. (a) 4 (b) 3 (c) 2 (d) 5 12) The VI curve for a diode shows (a) The amount of current for a given bias voltage (b) The voltage across the diode for a given current (c) The power dissipation (d) None of these 13) The depletion region in a diode consists of (a) Nothing but minority carriers (b) Majority carriers (c) Positive and negative ions (d) Answers (b) and (c) 14) What is the resistor value of an ideal diode in the region of conduction? (a) Undefined (b) 5 kω (c) 0 Ω (d) Infinity 15) The static (DC) resistance R D of a diode having I D = 30 ma and V D = 0.75 s (a) 0.04 Ω (b) 40 Ω (c) 25 Ω (d) Ω 16) The power dissipation of a 0.7 V silicon diode having I D = 40 ma equals (a) 28 W (b) 28 mw (c) 280 mw (d) Undefined 17) Determine the current in the following circuit (the diode is ideal). (a) 0 A (b) 4.76 ma (c) 5 A 15 V 3 kω (d) 5 ma 18) Determine the voltage across the resistor (a) 0 V (b) 0.09 V (c) 0.44 V 0.4 V (d) 0.4 V 3 kω 19) Determine I D (a) 0 ma (b) ma (c) ma (d) ma I D 12 V 5.6 kω Examiners: Dr. Tawfik Namour and Dr. Bassem Mokhtar page 3/5

4 20) For the circuit in figure 1, the value of the current in the resistor 3 kω is equal to: (a) 4 ma (b) 3.1 A (c) 3.1 ma (d) 0.67 ma 21) For the circuit in figure 2, = 157 V (peak), the dc output voltage is equal to: (a) 100 V (b) 50 V (c) 157 V (d) 0 V 22) If we change the polarity of the used diode in figure 2 and having = 157 V, the dc output voltage is equal to: (a) 50 V (b) 0 V (c) 157 V (d) 100 V 23) For the circuit shown in figure 3, if = 20 V, the output is equal to: (a) 2 V (b) 0 V (c) 18 V (d) 22 V 24) For the circuit shown in figure 3, if = 5 V, the output is equal to: (a) 0 V (b) 3 V (c) 5 V (d) 7 V 25) If the load resistance of a capacitorfiltered fullwave rectifier is reduced, the ripple voltage (a) Decreases (b) Increases (c) Is not affected (d) Has a different frequency 26) The peak value of the input to a halfwave silicon rectifier is 8 V. The peak value of the output is (a) 8.7 V (b) 8 V (c) 5.66 V (d) 7.3 V 27) A fullwave centertapped rectifying circuit with input voltage has peak value of 50 V will result in peak inverse voltage which approximately equals : (a) 50 V (b) 25 V (c) 100 V (d) 75 V 28) A fullwave bridge rectifying circuit with input voltage has peak value of 50 V will result in peak inverse voltage which approximately equals : (a) 25 V (b) 100 V (c) 50 V (d) 75 V 29) The circuit of figure 4 is considered: (a) Clamping circuit (b) Clipping circuit (c) Amplifying circuit (d) Filtering circuit 30) The input of the circuit of figure 4 is as follows : = 30 V for 0 < t < T/2, and = 30 V, for T/2 < t < T, where T is the signal period, the output for 0 < t < T/2 is: (a) 20 V (b) 10 V (c) 0 V (d) 30 V 31) The output of the circuit of figure 4 for T/2 < t < T is: (a) 30 V (b) 40 V (c) 35 V (d) 50 V 32) For the circuit of figure 5, the value of the Zener current is: (a) 10 ma (b) 10 A (c) 20 A (d) 20 ma 33) The maximum allowed input voltage for the network of figure 5 is: (a) 35 V (b) 30 V (c) 40 V (d) 50 V 34) The maximum power dissipated in the Zener diode shown in figure 5 is: (a) 200 mw (b) 300 mw (c) 400 mw (d) 100 mw Examiners: Dr. Tawfik Namour and Dr. Bassem Mokhtar page 4/5

5 35) The minimum load R L value for having operating Zener diode in figure 5 is: (a) Ω (b) Ω (c) Ω (d) Ω 36) There are two PN junctions in a bipolar transistor. Each one can be either forward biased (FB) or reverse biased (RB). In the linear active mode of operation, how are these two junctions biased? (a) Emitterbase is RB and basecollector is FB (b) Emitterbase is FB and basecollector is FB (c) Emitterbase is FB and basecollector is RB (d) Emitterbase is RB and basecollector is RB 37) Once in saturation, a further increase in base current will: (a) Cause the collector current to increase (b) Turn the transistor off (c) Cause the collector current to decrease (d) Not affect the collector current 38) In a certain biased npn transistor, V B is 2.95 V. The dc emitter voltage V E is approximately (a) 2.95 V (b) 2.25 V (c) 3.65 V (d) 0.7 V 39) In the circuit shown in figure 6 the value of I C is: (a) 100 A (b) 1 ma (c) 10 A (d) 100 ma 40) In the circuit shown in figure 6 the value of V C E is: (a) 15.7 V (b) 10 V (c) 5.7 V (d) 5.7 V 12V 3kΩ Figure 1 2V ideal Figure 2 2deal Figure 3 C ideal R 20V Figure 4 500Ω 25 V ZENER V Z = 10V, I Zmax = 30mA Figure 5 R L V CC = 15.7V 15kΩ R C =100 Ω β = 100 Figure 6 Examiners: Dr. Tawfik Namour and Dr. Bassem Mokhtar page 5/5

SEMICONDUCTOR ELECTRONICS: MATERIALS, DEVICES AND SIMPLE CIRCUITS. Class XII : PHYSICS WORKSHEET

SEMICONDUCTOR ELECTRONICS: MATERIALS, DEVICES AND SIMPLE CIRCUITS. Class XII : PHYSICS WORKSHEET SEMICONDUCT ELECTRONICS: MATERIALS, DEVICES AND SIMPLE CIRCUITS Class XII : PHYSICS WKSHEET 1. How is a n-p-n transistor represented symbolically? (1) 2. How does conductivity of a semiconductor change