Model Answer Electronics I. Final - Fall 2017 ECE201. MCQ Problems Total Q1 Q2 Q3 Q4

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1 Model Answer Course name: Eletronis I Exam number: Final - Fall 2017 Course Code: ECE201 Exam Date: Jan 2018 Leturer: Dr. Ahmed ElShafee Time Allowed: 120 minutes ID:... Name:.... MCQ Problems Total Q1 Q2 Q3 Q / 18 -

2 Part 1: MCQ Highlight your answer in the following table (answer only 20 questions) # A B C D E F G Answer 1 a 2 3 a a 8 b 9 10 d 11 b a 14 d a d 19 a 20 b b 23 a 24 a 25-2 / 18 -

3 (answer only 20 questions) # Question Answer 1 The proess of adding an impurity to an intrinsi semiondutor is a alled (a) doping (b) reombination () atomi modifiation (d) ionization 2 The majority arriers in an n-type semiondutor are (a) holes (b) valene eletrons () ondution eletrons (d) protons 3 The minority arriers in an n-type semiondutor are a (a) holes (b) valene eletrons () ondution eletrons (d) protons 4 The purpose of a pentavalent impurity is to (a) redue the ondutivity of silion (b) inrease the number of holes () inrease the number of free eletrons (d) reate minority arriers 5 Eah atom in a silion rystal has (a) four valene eletrons (b) four ondution eletrons () eight valene eletrons, four of its own and four shared (d) no valene eletrons beause all are shared with other atoms 6 If the PIV rating of the diodes in Figure is inreased, the urrent through RL will (a) inrease (b) derease () not hange 7 When a 60 Hz sinusoidal voltage is applied to the input of a full-wave a - 3 / 18 -

4 retifier, the output frequeny is (a) 120 Hz (b) 60 Hz () 240 Hz (d) 0 Hz 8 When the peak output voltage is 100 V, the PIV for eah diode in a enter-tapped full-wave retifier is (negleting the diode drop) (a) 100 V (b) 200 V () 141 V (d) 50 V 9 If the frequeny of the input voltage in Figure is inreased, the output voltage will b (a) inrease (b) derease () not hange 10 The total seondary voltage in a enter-tapped full-wave retifier is 125 V rms. Negleting the diode drop, the rms output voltage is (a) 125 V (b) 177 V () 100 V (d) 62.5 V d - 4 / 18 -

5 11 b 12 If R in Figure is inreased, the urrent to the load resistor will (a) inrease (b) derease () not hange If the input voltage amplitude in Figure is redued, the amplitude of the output voltage will (a) inrease (b) derease () not hange 13 The athode of a zener diode in a voltage regulator is normally (a) more positive than the anode (b) more negative than the anode () at +0.7 V (d) grounded 14 A no-load ondition means that (a) the load has infinite resistane (b) the load has zero resistane () the output terminals are open (d) answers(a) and () 15 An LED (a) emits light when reverse-biased (b) senses light when reverse-biased () emits light when forward-biased (d) ats as a variable resistane a d - 5 / 18 -

6 16 a 17 If a transistor with a higher β DC is used in Figure, the olletor urrent will (a) inrease (b) derease () not hange If VCC in Figure is inreased, the base urrent will (a) inrease (b) derease () not hange 18 The three terminals of a bipolar juntion transistor are alled (a) p, n, p (b) n, p, n () input, output, ground (d) base, emitter, olletor 19 The βdc of a transistor is its (a) urrent gain (b) voltage gain () power gain (d) internal resistane d a - 6 / 18 -

7 20 b If VBB is redued in Figure, the olletor urrent will (a) inrease (b) derease () not hange 21 When a lowerase (r) is used in relation to a transistor, it refers to (a) a low resistane (b) a wire resistane () an internal a resistane (d) a soure resistane 22 b If the amplitude of Vin in Figure is dereased, the a output voltage amplitude will (a) inrease (b) derease () not hange - 7 / 18 -

8 23 a 24 RC in Figure is redued in value, the value of IC will (a) inrease (b) derease () not hange a If the emitter in Figure beomes disonneted from ground, the olletor voltage will (a) inrease (b) derease )) not hange 25 In saturation, VCE is (a) 0.7 V (b) equal to VCC () minimum (d) maximum - 8 / 18 -

9 Part 2: problems: Q Consider the iruit in Figure. 1 (a) What type of iruit is this? (b) What is the total peak seondary voltage? () Find the peak voltage aross eah half of the seondary. (d) Sketh the voltage waveform aross RL. (e) What is the peak urrent through eah diode? (f) What is the PIV for eah diode? [5 points] - 9 / 18 -

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11 Q2 The transistor in figure has the following maximum ratings PD(max) = 800 mw, VCE(max)=15V and IC(max)=100 ma. Determine the maximum value to whih VCC an be adjusted without exeeding Rating, whih rating would be exeeded first? [5 points] - 11 / 18 -

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13 Q3 To what value must R be adjusted in Figure to make I Z = 40 ma? Assume Vz=12V, at 30 ma and Zz=30 ohm. A 20 V peak sinusoidal voltage is applied to that iruit in Figure in plae of the d soure. Draw the output waveform. [5 points] - 13 / 18 -

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15 Q 4 For the following data sheet of zener diodes, as 1N4736A zener diode has a Zz=3.5 ohm. The data sheet gives Vz=6.8 V, at a test urrent Iz=37A. what is the voltage aross the zener terminals when the urrent is 55 ma? When the urrent is 20 ma? [5 points] - 15 / 18 -

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TRANSISTORS: DYNAMIC CIRCUITS. Introduction

TRANSISTORS: DYNAMIC CIRCUITS. Introduction TRANSISTORS: DYNAMIC CIRCUITS Introdution The point of biasing a iruit orretly is that the iruit operate in a desirable fashion on signals that enter the iruit. These signals are perturbations about the