Electronic Devices 1- Semicon To Diodes

Question 1

A silicon diode measures a low value of resistance with the meter leads in both positions. The trouble, if any, is
the diode is open.
the diode is shorted to ground.
the diode is internally shorted.
the diode is working correctly.

Answer 1

the diode is internally shorted.

Question 2

Single-element semiconductors are characterized by atoms with ____ valence electrons.
3
4
5
2
none of the above

Answer 2

4

Question 3

Under normal conditions a diode conducts current when it is
reverse-biased.
forward-biased.
avalanched.
saturated.

Answer 3

forward-biased

Question 4

A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.
positive supply
negative supply
cathode
anode

Answer 4

positive supply

Question 5

As the forward current through a silicon diode increases, the internal resistance
increases.
decreases.
remains the same.

Answer 5

decreases

Question 6

The movement of free electrons in a conductor is called
voltage.
current.
recombination.
equilibrium.

Answer 6

current

Question 7

For a forward-biased diode, the barrier potential ________ as temperature increases.
decreases
remains constant
increases

Answer 7

decreases

Question 8

The wide end arrow on a schematic indicates the ________ of a diode.
ground
direction of electron flow
cathode
anode

Answer 8

anode

Question 9

An n-type semiconductor material
is intrinsic.
has trivalent impurity atoms added.
has pentavalent impurity atoms added.
requires no doping.

Answer 9

has pentavalent impurity atoms added.

Question 10

For a forward-biased diode, as temperature is ________, the forward current ________ for a given value of forward voltage.
decreased, increases
increased, increases
increased, decreases
decreased, decreases

Answer 10

increased, increases

Question 11

Which statement best describes an insulator?

Answer 11

A material with few free electrons.

Question 12

Effectively, how many valence electrons are there in each atom within a silicon crystal?

Answer 12

8

Question 13

The boundary between p-type material and n-type material is called

Answer 13

a pn junction.

Question 14

You have an unknown type of diode in a circuit. You measure the voltage across it and find it to be 0.3 V. The diode might be

Answer 14

a germanium diode.

Question 15

An ideal diode presents a(n) ________ when reversed-biased and a(n) ________ when forward-biased.

Answer 15

open, short

Question 16

A reverse-biased diode has the ________ connected to the positive side of the source, and the ________ connected to the negative side of the source.

Answer 16

cathode, anode

Question 17

What types of impurity atoms are added to increase the number of conduction-band electrons in intrinsic silicon?

Answer 17

pentavalent

Question 18

What factor(s) do(es) the barrier potential of a pn junction depend on?

Answer 18

type of semiconductive material
the amount of doping
the temperature
-all of the above

Question 19

An atom is made up of

Answer 19

protons.
neutrons.
electrons.
all of the above

Question 20

Reverse breakdown is a condition in which a diode

Answer 20

is subjected to a large reverse voltage.

Question 21

There is a small amount of current across the barrier of a reverse-biased diode. This current is called

Answer 21

reverse leakage current.

Question 22

As the forward current through a silicon diode increases, the voltage across the diode

Answer 22

is relatively constant.

Question 23

Doping of a semiconductor material means

Answer 23

that impurities are added to decrease the resistance of the material.

Question 24

The forward voltage across a conducting silicon diode is about

Answer 24

0.7 V

Question 25

The most common type of diode failure is a(n)

Answer 25

open

Question 26

What occurs when a conduction-band electron loses energy and falls back into a hole in the valence band?

Answer 26

recombination

Question 27

The maximum number of electrons in each shell of an atom is

Answer 27

2n2 where n is the number of the shell.

Question 28

A silicon diode is forward-biased. You measure the voltage to ground from the anode at ________, and the voltage from the cathode to ground at ________.

Answer 28

2.3 V, 1.6 V

Question 29

The term bias in electronics usually means

Answer 29

the value of dc voltages for the device to operate properly.

Question 30

One eV is equal to ________ J.

Answer 30

1.6 × 10–19

Question 31

The diode ________.

Answer 31

is the simplest of semiconductor devices has characteristics that closely match those of a simple switch is a two-terminal device -All of the above

Question 32

What does a high resistance reading in both forward- and reverse-bias directions indicate?

Answer 32

An open diode

Question 33

Which capacitance dominates in the reverse-bias region?

Answer 33

depletion

Question 34

What is the state of an ideal diode in the region of nonconduction?

Answer 34

An open circuit

Question 35

How many orbiting electrons does the germanium atom have?

Answer 35

32

Question 36

How many terminals does a diode have?

Answer 36

2

Question 37

What unit is used to represent the level of a diode forward current IF?

Answer 37

mA

Question 38

The diffused impurities with ________ valence electrons are called donor atoms.

Answer 38

5

Question 39

In which of the following color(s) is (are) LEDs presently available?

Answer 39

Yellow White Orange All of the above

Question 40

What is the range of the operating voltage level for LEDs?

Answer 40

1.7–3.3 V

Question 41

At what kind of operating frequency diffusion or transition is a capacitor represented in parallel with the ideal diode?

Answer 41

Very high frequency

Question 42

Which of the following devices can check the condition of a semiconductor diode?

Answer 42

Digital display meter (DDM) Multimeter Curve tracer All of the above

Question 43

Which of the following is an atom composed of?

Answer 43

Electrons Protons Neutrons All of the above

Question 44

The condition of a semiconductor diode can be determined quickly using a ________.

Answer 44

DDM VOM curve tracer Any of the above

Question 45

How many valence electrons does a silicon atom have?

Answer 45

4

Question 46

What is the resistor value of an ideal diode in the region of conduction?

Answer 46

0

Question 47

Calculate the power dissipation of a diode having ID = 40 mA.

Answer 47

28 mW

Question 48

Calculate static resistance RD of a diode having ID = 30 mA and VD = 0.75 V.

Answer 48

Using Ohm' law V= iR. 0.75mV= 40 mA * R. We gets, R = 25 V/A, R = 25 ohms.

Question 49

In which of the following is the light intensity measured?

Answer 49

Candela

Question 50

Calculate ID if RD = 30 and VD = 0.84 V.

Answer 50

ID = VD/RD. ID = 0.84/30. ID = 0.028 A (Converting A into mA. Then multiply by 1000). ID = 0.028*1000 = 28 mA.

Question 51

Which of the following elements is most frequently used for doping pure Ge or Si?

Answer 51

Boron Gallium Indium All of the above

Question 52

Calculate the temperature coefficient in %/° C of a 10-V nominal Zener diode at 25° C if the nominal voltage is 10.2 V at 100° C.

Answer 52

V1 = 10 V. T1 = 25 c. V2 = 10.2 V. T2 = 100 c. Then temperature coefficient is = [{(V2-V1)/V1}/(T2-T1)]*100. = [(10.2-10/10)/(100-25)]*100. = 0.0267 V.

Question 53

In general, LEDs operate at voltage levels from ________ V to ________ V.

Answer 53

1,7, 3.3

Question 54

Determine the nominal voltage for the Zener diode at a temperature of 120° C if the nominal voltage is 5.1 volts at 25° C and the temperature coefficient is 0.05%/° C.

Answer 54

Vf = Vi * [1 + (Coeff / 100)*(Tf - Ti)], Vf = 5.1*[1 + (0.05/100)*(120-25)], Vf = 5.43225 V.

Question 55

What is the maximum power rating for LEDs?

Answer 55

150 mW

Question 56

The ________ diode model is employed most frequently in the analysis of electronic systems.

Answer 56

simplified

Question 57

What is the value of the transition capacitance for a silicon diode when VD = 0? (Choose the best answer.)

Answer 57

3 pF

Question 58

Which of the following ratings is true?

Answer 58

Si diodes have higher PIV and wider temperature ranges than Ge diodes.

Question 59

The ideal diode is a(n) ________ circuit in the region of nonconduction.

Answer 59

open

Question 60

Which capacitance dominates in the forward-bias region?

Answer 60

Diffusion

Question 61

In what state is a silicon diode if the voltage drop across it is about 0.7 V?

Answer 61

Forward bias

Question 62

Schottky diodes are also known asSchottky diodes are also known as

Answer 62

hot carrier diodes.

Question 63

Zener diodes with breakdown voltages less than 5 V operate predominantly in what type of breakdown?

Answer 63

zener breakdown

Question 64

The Schottky diode is used

Answer 64

in very fast-switching circuits.

Question 65

You have an application for a diode to be used in a tuning circuit. A type of diode to use might be

Answer 65

a varactor

Question 66

What kind of diode is formed by joining a doped semiconductor region with a metal?

Answer 66

Schottky

Question 67

Which diode employs graded doping?

Answer 67

step-recivery

Question 68

LEDs are made out of

Answer 68

gallium

Question 69

The normal operating region for a zener diode is the

Answer 69

reverse-breakdown region.

Question 70

An LED is forward-biased. The diode should be on, but no light is showing. A possible trouble might be

Answer 70

the diode is open.

Question 71

A 6.2 V zener is rated at 1 watt. The maximum safe current the zener can carry is

Answer 71

Iz=P/Vz Iz=1/6.2 Iz=0.161A Iz=161mA

Question 72

The process of emitting photons from a semiconductive material is called

Answer 72

electroluminescence

Question 73

What diode operates only with majority carriers?

Answer 73

Schottky

Question 74

An 8.2 V zener has a resistance of 5. The actual voltage across its terminals when the current is 25 mA is

Answer 74

Vz = 8.2 V. Rs = 5 ohms. Is = 25 mA = 0.025 A. Vs = Is x Rs. = 0.025 x 5 = 0.125 V. Vin = Vz+Vs. = 8.2 V + 0.125 V. = 8.325 V answer.

Question 75

What type of diode maintains a constant current?

Answer 75

current regulator

Question 76

What diode is used in seven-segment displays?

Answer 76

LED

Question 77

Zener diodes with breakdown voltages greater than 5 V operate predominantly in what type of breakdown?

Answer 77

avalanche

Question 78

Back-to-back varactor diodes are used for what reason?

Answer 78

to eliminate harmonic distortion

Question 79

A tunnel diode is used

Answer 79

in circuits requiring negative resistance.

Question 80

What type of diode is commonly used in electronic tuners in TVs?

Answer 80

varactor

Question 81

A laser diode normally emits

Answer 81

coherent and monochromatic light.

Question 82

A varactor is a pn junction diode that always operates in ________-bias and is doped to ________ the inherent capacitance of the depletion region.

Answer 82

reverse, maximize

Question 83

What type of diode circuit is used to clip off portions of signal voltages above or below certain levels?

Answer 83

clipper or limiter

Question 84

Each diode in a center-tapped full-wave rectifier is ________ -biased and conducts for ________ of the input cycle.

Answer 84

forward, 180º

Question 85

The output frequency of a full-wave rectifier is ________ the input frequency.

Answer 85

twice

Question 86

PIV is which of the following?

Answer 86

peak inverse voltage

Question 87

In a regulated supply, what term describes how much change occurs in the output voltage for a given change in the input voltage?

Answer 87

line regulation

Question 88

A short circuit has a ________ drop across its terminals, and the current is limited only by the surrounding network.

Answer 88

0 V

Question 89

What type of diode circuit is used to add or restore a dc level to an electrical signal?

Answer 89

clamper

Question 90

In a regulated supply, what term describes how much change occurs in the output voltage over a certain range of load current values, from minimum to maximum current?

Answer 90

load regulation

Question 91

What is the PIV for each diode in a full-wave center-tapped rectifier? Note: Vp(out) = peak output voltage.

Answer 91

2Vp(out) + 0.7 V

Question 92

If the ac supply is 50 Hz, what will be the ripple frequency out of the full-wave rectifier?

Answer 92

100 Hz

Question 93

How many terminals do the 7800 series fixed positive voltage regulators have?

Answer 93

3

Question 94

An open circuit can have any voltage across its terminals, but the current is always ________.

Answer 94

0 A

Question 95

A silicon diode in a half-wave rectifier has a barrier potential of 0.7 V. This has the effect of

Answer 95

reducing the peak output voltage by 0.7 V.

Question 96

In the operation of a half-wave rectifier with a capacitor-input filter, the ripple factor can be lowered by ________ the value of the filter capacitor or ________ the load resistors.

Answer 96

increasing, increasing

Question 97

In a particular problem, which mode has the highest level of IDQ?

Answer 97

Ideal

Question 98

Which diode(s) has (have) a zero level current and voltage drop in the ideal model?

Answer 98

Both Si and Ge

Question 99

The output frequency of a half-wave rectifier is ________ the input frequency.

Answer 99

equal to

Question 100

A diode is in the "________" state if the current established by the applied sources is such that its direction matches that of the arrow in the diode symbol, and VD ≥ 0.7 V for Si and VD ≥ 0.3 V for Ge.

Answer 100

on

Question 101

List the categories of clippers.

Answer 101

Series and parallel

Question 102

A silicon diode has a voltage to ground of –117 V from the anode. The voltage to ground from the cathode is –117.7 V. The diode is

Answer 102

forward-biased.

Question 103

In a voltage regulator network with fixed RL and R, what element dictates the minimum level of source voltage?

Answer 103

Vz