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Electronics > Exam review > Flashcards

Exam review Flashcards

1
Q

An atom of a material used as a conductor generally contain how many valence electrons?

A

1, 2 or 3

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2
Q

How many layers of semi conductor make up a bipolar junction transistor

A

3 layers

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3
Q

Name 3 terminals of Bipolar junction transistor?

A

Base, collector, emitter.

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4
Q

Name 2 types of BJT?

A

NPN , PNP

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5
Q

An atom of a material used as a insulator contain how many valence electrons?

A

7 to 8 valence electrons.

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6
Q

What activated a BJT?

A

current activated

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7
Q

An atom of a material used as a semi-conductor contain how many valence electrons?

A

4 valence electrons

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8
Q

what is the polarity of the emitter in a NPN Transistor?

A

Negative polarity

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9
Q

Base current of a BJT is 20 micro amps and the beta number is 275
calculate the emitter current

A

IEmitter = I base x (beta+1)
= 20 micro amps x (275 =1)
= 5.52 milli amps
or
IEmitter = I base + I current
= 20 micro amps + (275 x 20 micr amps)
=5.52 micro amps

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10
Q

What activates a UJT and PUT

A

voltage activated

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11
Q

what are the terminals lablled in a UJT

A

BI
B2
Emitter

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12
Q

Collector current at BJT equals 2.4 milli amps and Emitter current equals 4.515 milli amps
calculate beta number?

A

IB = IE - IC
= 4.515 mA - 4.5 mA
= 15 micro amps

Beta = IC / IB
= 4.5 mA / 15 Micro amps
300

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13
Q

When P-type material is made an impurity is added to pure silicon or germanium. how many valence electrons will the impurity have?

A

P -type = 3

if it were N-type = 4

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14
Q

What type of semiconductor material can withstand a great amount of heat?

A

silicon

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15
Q

What is the polarity of the basse on a PNP

A

negative polarity

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16
Q

What determines the impedance of a bipolar junction?

A

amount of current flow

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17
Q

What is the voltage polarity of the collector terminal in a NPN?

A

Positive Polarity

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18
Q

What determines the collecter current in a NPN

A

IC = Beta x Base current (b x IB)

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19
Q

A npn transistor has a base current of 10 micro amps and a beta number of 250
calculate collector current

A

IC = beta x base current
= 250 x 10 micro amps
= 2.5 mA

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20
Q

When a bipolar junction transistor is said to be completely turned on, what is the voltage drop between the controller emitter?

A

0.7 volts

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21
Q

When a transistor is driven into saturation, what is the voltage drop between the collector emitter ?

A

0.3 volts

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22
Q

How is a transistor driven into saturation ?

A

Increased base current (IB) that is needed for normal operation .

23
Q

Why is it desirable to drive a transistor into saturation mode ?

A

Produce less heat

24
Q

What is a disadvantage of driving a transistor into saturation

A

Less frequency used / switch reduced

25
Q

How many layers of a semiconductor material are used in a UJT?

A

2 layers

26
Q

How many primary layers of a semiconductor wre used in a PUT ?

A

4 layers . 2 p’s and 2 N’s

27
Q

In a darlington transistor has 15 micro amps flowing into the base of the driver transistor and 135 mA is flowing into the collector of the power transistor .
What is the beta number of the darlington ?

A

B = IC / IB
= .135 a / .000015
= 9000

28
Q

How is a darlington amplifier constructed ?

A

Connecting the emitter of the driver transistor to the base of power transistor

29
Q

The SCR is a member of what electronic family ?

A

Thyristers

30
Q

What activates the UJT and PUT transistors?

A

Voltage activated

31
Q

How many layers of a semiconductor are used t make a SCR?

A

4 layers

32
Q

Whate are the terminal names for a PUT?

A

Anode
Cathode
Gate

33
Q

What are the terminals of UJT?

A

B1
B2
Emitter

34
Q

what are the terminal names of SCR?

A

Anode
Cathode
Gate

35
Q

What are the terminal names of a BJT?

A

Base
collecter
emitter

36
Q

What activates a BJT?

A

Current activated

37
Q

SCR stands for?

A

Silicon controlled rectifier?

38
Q

BJTs 2 general uses are

A

Switching and amplifying

39
Q

A Bipolar junction transistor is connected INTO A CIRCUIT as an AMPLIFIER.
A power supply supplies 16 volts to the transistor ALWAYS HALF.
When biasing (pre setting the transistor, how much voltage should be dropped across the collector-emitter section of the transmitter?

A

16 volts / 2 = 8 volts

Amplifier = half the voltage

40
Q

Name the 2 types of BJT.

A

NPN = 2 positive terminals and 1 negative terminal

PNP - 2 negative terminals and 1 positive terminal.

41
Q

When a transistor is said to be completely turned off. What is the Voltage drop between collector-emitter?

A

0.7 voltage drop

42
Q

When a trnsistor is driven into saturation mode what is the voltage drop between the collecter-emitter?

A

0.3 volts

43
Q

How is a transistor driven into saturation?

A

Increased base current

44
Q

What is the disadvantage of a driver to the transistor?

A

Less frequency and reduced switching

45
Q

Why is it desirable to drive a transistor into saturation ?

A

Produes less heat.

46
Q

BJT’s must be biased when connected to a power supply.
What is the bias between the base-emitter?
B E
N P N
+ -

A

Forward bias

47
Q

BJT’s must be biased when connected to a power supply.
What is the bias between the base-emitter?
B E
N P N
+ -

A

Forward bias

48
Q

In a BJT, if the base current equals 40 micro amps and emitter- current equals 11.24 mA, then what is beta ?

A

IB = 40 micro amps IC = IE - IB
IE = 11.24 mA IC = 11.24 mA - 40 micro
B = IC / IB IC = 11.2 mA
B = 11.2 mA /40 micro amps
B = 280

49
Q

Calculate current equals 3 milli amps and emitter-current equals 3.01 milli amps
Calculate the Beta #

A

IC = 3 mA
IE = 3.01 miA
IB = IE - IC
= 3.01 mA - 3mA
= 10 micro amps
B = IC / IB
= 3.01mA / 10 micro amps.

50
Q

What is the polariity of the collector terminal in a PNP transistor ?

A

Negative polarity

51
Q

electrons in a valence shell used as a conductor ?

A

1 to 3

52
Q

electrons in a valence shell of an insulator?

A

7or 8

53
Q

electrons in a valence shell of a semi conductor ?

A

4

Electronics (4 decks)

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