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Physics Class 12 > Semiconductor Electronics > Flashcards

Semiconductor Electronics Flashcards

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1
Q

What happens to covalent bond when temp is high?

A

Bond breaks, & e’ go to conduction band

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2
Q

What happens to intrinsic semiconductor at 0K?

A

It behaves as insulator

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3
Q

What is intrinsically created e’s?

A

e’s due to breaking of covalent bond

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4
Q

Types of extrinsic semiconductors

A

p & n type

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5
Q

When is a semiconductor extrinsic?

A

When impurities are added and conductivity is increased

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6
Q

n type of impurities

A

pentavalent

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7
Q

pentavalent is also called

A

donors

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8
Q

p type of impurities

A

trivalent

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9
Q

metal have _____ resistivity

A

low

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10
Q

semiconductors have _____ resistivity

A

intermediate to metals & insulators

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11
Q

Elemental semiconductors

A

Silicon & Germanium

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12
Q

Valence band

A

Band which includes the energy levels of the valence electrons

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13
Q

conduction band

A

Band above valence band

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14
Q

In intrinsic semiconductors, the number of free
electrons, ne is __________ the number of holes, nh

A

equal to

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15
Q

Doping

A

Addition of impurities

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16
Q

Dopants

A

Impurity atoms

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17
Q

2 things before formation of P N junc diode?

A

Diffusion & drifting

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18
Q

In diffusion, e’ moves from

A

n to p

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19
Q

In drifting, e’s move from

A

p to n

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20
Q

Diffusion current & drifting current are always

A

opposite

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21
Q

Depletion region?

A

Space-charge region on either side of the junction together

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22
Q

What happens due to +ve space-charge region on n side and -ve space-charge on p-side?

A

electric field directed from positive charge towards negative charge develops

23
Q

What is drifting?

A

The motion of minority charge
carriers due to the electric field

24
Q

As the diffusion process continues, the space-charge regions on either side

A

increases

25
Q

When space charge region increase, EF & drift current

A

increases

26
Q

In a p-n junction under equilibrium there
is _____ net current

A

no

27
Q

Barrier potential

A

Potential that tends to prevent the movement of
e’ from the n to p

28
Q

In forward bias, as applied voltage increases

A

depletion width and effective barrier decreases

29
Q

When applied voltage is less, barrier potential and current

A

reduces slightly below eq. level; will be less

30
Q

Minority carrier injection

A

e’ from n-side cross depletion region reach p side where they are minority

31
Q

In reverse bias, barrier potential & effective barrier value

A

increases

32
Q

In reverse bias, diffusion current

A

decreases

33
Q

Diode reverse current is not very much dependent on

A

applied voltage

34
Q

threshold voltage

A

Voltage at which current starts increases

35
Q

threshold voltage for Si

A

0.7V

36
Q

threshold voltage for Ge

A

0.2V

37
Q

Reverse saturation current

A

Current which remains const with change in bias

38
Q

Rectification?

A

Conversion of AC to DC

39
Q

Types of rectifiers

A

Full & half wave recifiers

40
Q

When only will a diode conduct?

A

In forward bias

41
Q

Why can’t Ge & Si be used to make LEDs

A

Their energy gap is very less

42
Q

Colour of LED is due to

A

energy gap

43
Q

2 Types of transistors

A

npn & pnp

44
Q

BJT full form

A

Bipolar Junction Transistor

45
Q

Which is an efficient circuit for getting rectified voltage?

A

full wave rectifier

46
Q

Rectified voltage is _____ direcitonal

A

Uni

47
Q

How to get a steady DC output?

A

Capacitor/Inductor is connected across the output terminals || to load

48
Q

What are filters?

A

Those filter out the ac ripple and give a pure dc voltage

49
Q

What happens when voltage across capacitor increases?

A

Rectifier gets charged

50
Q

Why should large capacitors be used?

A

To make the time constant large, value of
C should be large

51
Q

What is used to make LEDs?

A

GaAs

52
Q

Use of LEDs?

A

Remote controls, burglar alarm systems,
optical communication

53
Q

LED vs incandescent low power lamps:

A

Low operational voltage & less power.
Fast action and no warm-up time required
Long life and ruggedness
Fast on-off switching capability

Physics Class 12 (14 decks)

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