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B1 4- Electronic Fundamentals > 4.1.1 Semiconductors > Flashcards

4.1.1 Semiconductors Flashcards

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1
Q

What is a diode?

A

A two terminal electronic component which conducts current in a single direction

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2
Q

How does a diode conduct current in a single direction?

A

By applying low resistance in one direction and a high resistance in the other

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3
Q

On a schematic of a diode what does the arrow indicate?

A

The anode side (positive side)

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4
Q

On a schematic of a diode what does the bar end indicate?

A

The cathode side (negative side)

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5
Q

What are diodes vulnerable to in handling and operation?

A

Electro-static discharge

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6
Q

What are some of the key characteristics of diodes?

A

-small size and weight
-low operating voltages
-lower power dissipation
-high reliability
-long service life

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7
Q

What are diodes made from?

A

Semiconductors

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8
Q

How can a semiconductors properties change their conductivity?

A

-change in temperature
-change in light intensity
-purity content

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9
Q

Does a semiconductor act as a conductor or insulator?

A

They can function as either depending on the operational conditions

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10
Q

What does PN stand for in a PN junction diode?

A

Positive-negative

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11
Q

How is a positive-negative junction diode fabricated?

A

Doping two sides of a single crystal semiconductor with opposite types of impurities

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12
Q

What are the two sides of a positive-negative junction diode called?

A
  • P-type (positive)
  • N-type (negative)
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13
Q

What is special about the electrons on a N-type material?

A

They have excess electrons

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14
Q

What is special about electrons in a P-type material?

A

It is lacking electrons

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15
Q

A P-type material is lacking electrons but what is said about the ‘holes’?

A

It has an excess of holes which the electrons can move into

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16
Q

Where is a depletion layer formed?

A

When P-type and N-type materials are bonded together

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17
Q

What is the depletion layer sometimes known as?

A

Barrier region

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18
Q

When a P-type material is connected to the positive side of a battery. What is this called?

A

Forward bias

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19
Q

What is it called when a P-type material is connected to the negative side of a battery?

A

Reverse bias

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20
Q

When diode are connected in series what happens?

A

The forward current flowing through each diode must be the same

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21
Q

When diodes are connected in series why must you not exceed any individual diode current rating?

A

As the forward current flowing through each diode is the same

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22
Q

What happens to voltage when it goes through a diode?

A

It has a small voltage drop

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23
Q

What is the voltage drop of a germanium diode?

A

0.3 V

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24
Q

What is the voltage drop in silicon diodes?

A

0.7 V

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25
What is forward voltage of a diode?
The voltage you have after it has passed through the diode
26
What happens when diodes are connected in parallel?
They share the current equally
27
What’s the aim problem of connecting diodes in parallel?
Because they share the load when one fails the others have to pick up more load which increases the stress on the others
28
When will diodes connected in parallel not conduct current equally?
If they have different forward bias characteristics
29
If diodes are connected in parallel what diodes should be used where possible?
Identical diodes
30
What is a silicon controlled rectifier (SCR) also known as?
Thyristor
31
What is the build up of a thyristor?
A multi-layered semiconductor device with at least four layers of alternating N- and P- type material
32
How many P-N junctions are in a thyristor?
3 (due two having 4 materials connected together)
33
How many hertz does a thyristor go up to?
400Hz
34
What are the 3 operating states of a thyristor?
-reverse blocking mode -forward blocking mode -forward conducting mode
35
What happens if a thyristors maximum current is exceeded?
The thyristor will be destroyed
36
What is an LED?
Light emitting diode
37
Electronic components that emit light are known as?
Optoelectronic components
38
What are LEDs mainly used for?
As sensors or signalling devices
39
How does an LED work?
When an electron recombines with a hole they emit energy in the form of photons
40
What determines the colour of an LED?
The semiconductor material used
41
What does the switching time of an LED range between?
50-400 nanoseconds
42
LEDs in the visible light range are manufactured from?
Gallium Arsenide Phosphide (GaAsP) and Gallium Phosphide (GaP)
43
LEDs that emit infrared light are made from?
Gallium Arsenide (GaAS) combinations with minimal amounts of zinc and silicon
44
What colour LED is industry standard for signalling and indicating?
Red
45
What is a photo-conductive diode?
A diode that reacts to light
46
What does a photo-conductive diode respond to better than visible light?
Red and infra-red
47
What are Varistor also called?
VDRs (voltage Dependant Resistors)
48
What makes up the semiconductor layer of a Varistor?
Highly conducive crystal particles, each of which is covered with an extremely thin barrier layer and sintered together
49
In Varistor what is the resistance level inversely proportional to?
The voltage applied (irrespective of polarity)
50
What are Varistor mainly used for?
To protect systems against excess voltage
51
What are rectifier diodes used for?
Turning AC into DC
52
A recognisable feature of the larger rectifier diodes is that they are encased in metal, why is this?
The metal acts as a heat sink
53
When a diode is wire incorrectly what will a multimeter read?
A very high resistance (open circuit)
54
What does it mean if testing a diode and the multimeter reads high resistance in both orientations?
The diode is faulty and should be replaced
55
What does it mean if a diode shows low resistance in both orientations?
It has short circuited
56
When a multimeter is set to the diode test position, what is the applied voltage?
Approximately 2.5-3.5 volts
57
On a multimeter what will a serviceable diode read?
0.6 - 0.7 Volts
58
On a multimeter what will a diode in the reverse bias direction (wrong orientation) read?
Overload (OL)
59
On a multimeter what will a diode read if it has short circuited?
Zero (or very close to zero)
60
What are transistors widely used for?
Switching and controlling current within a circuit
61
How do transistors control their switching on and off?
By using small digital and analogue signals
62
What material is used to make transistors?
Semiconductors such as: -silicon -germanium -gallium-arsenide
63
What are transistors classified into?
-junction transistors -field effect transistors
64
What is the basic transistor?
Bipolar junction transistor
65
How many depletion areas does a bipolar junction transistor have?
2 because it has 3 parts of P/N-type material
66
What are the names of each terminal in a bipolar junction transistor?
-emitter (E) -base (B) -Collector (C)
67
How is current controlled in a field effect transistor?
By the action of a an electron field
68
What is a integrated circuit?
A combination of several electronic components in a common housing
69
What is a disadvantage of a integrated circuit?
Because everything is tightly packed together it will need additional cooling
70
What is the biggest disadvantage of a integrated circuit?
They cant be repaired and must be replaced
71
What components are found in integrated circuits?
-transistors/diodes -resistors -capacitors
72
Why cant inductances be used in a integrated circuit?
Due to their large space requirements
73
What do logic gates do?
Perform desired functions when information is input
74
What is a NOT gate also known as?
An Inverter
75
What does a NOT gate do?
Inverts the signal
76
What does a AND gate do?
Only operate when all signals are true
77
How does a OR gate work?
It only needs one of any inputs to be true t produce an output
78
What is a NAND gate?
When a NOT and an AND gate are combined (so when all inputs are the same an output is produced but inverted)
79
What is an NOR gate?
It’s an inverted OR gate
80
What is an XOR gate?
When both inputs are the same you don’t have an output. Vice Versa
81
What is an another name for an XOR gate?
Exclusive gate
82
What are analogue integrated circuits?
Integrated circuits that operate over an entire range of continuous values of the signal amplitude
83
What are the two types of analogue integrated circuits?
-linear integrated circuits -radio frequency integrated circuits
84
What is a linear circuit?
When a circuits output is directly proportional to the input
85
What is the most used linear integrated circuit?
An operational amplifier
86
What is an operational amplifier also known as?
Op-Amp
87
How many inputs does an op-amp have?
Two (one inverting and one non-inverting)
88
What is the purpose of a op-amp?
To amplify and output the voltage difference between the two input pins
89
On an op-amp what side is the negative called?
Inverting input
90
On an op-amp what is the positive side called?
Non-inverting input
91
Which direction are the pins numbered on an integrated circuit?
Anti-clockwise
92
How can pin 1 be identified on an integrated circuit?
By a dot marked on the body
93
If there is a notch on a integrated circuit an no dot marker how do you find pin one?
Turn the board so that the notch is on the left and then pin 1 will be bottom left
94
How many pins does a integrated circuit with a op-amp installed require on a minimum?
7 pins (the circuit will have 8 where one isn’t used)
95
When feedback is placed on the non-inverting input, what status does the feedback come out as?
Positive
96
When feedback is placed on the inverting input, what status does the feedback come out as?
Neegative
97

B1 4- Electronic Fundamentals (4 decks)

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