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Level 4 : Electronics > Specials Diodes > Flashcards

Specials Diodes Flashcards

1
Q

What does SCR stand for?

A

Silicon Controlled Rectifier

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2
Q

What kind of feedback does SCR use?

A

uses Regenerative feedback

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3
Q

What is Regenerative Feedback?

A

part of the output is returned to the input to reinforce the input power

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4
Q

How many layers are in an SCR and what are the materials?

A

four layers and alternating p-type and n-type material

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5
Q

what are the three electrodes of an SCR

A
  1. Anode
  2. Cathode
  3. Gate
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6
Q

What direction is an SCR?

A

undirectional device

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7
Q

Is SCR current or voltage operated?

A

current operated

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8
Q

Can an SCR control and switch AC and/or DC power

A

YES

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9
Q

Does SCR rectify AC or DC

A

AC

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10
Q

SCR
What is lathing current?

A

current must be applied to start conduction

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11
Q

SCR
What is holding current?

A

current must be maintained for SCR to remain in conduction

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12
Q

SCR
What is Voltage Break Over(VBO)

A

forward voltage that puts SCR into conduction

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13
Q

SCR
What is Voltage Break Over(VBO)

A

the forward voltage required to put SCR into conduction

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14
Q

SCR
What is Voltage Break Over(VBO)

A

the forward voltage that puts SCR into conduction

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15
Q

What is the structure of the SCR

A

consists of two PN junctions to form a PNPN Layer

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16
Q

What is the normal state for SCR

A

Forward Blocking State

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17
Q

The forward blocking state allows the SCR to conduct if one of the two conditions apply

A
  1. Exceed VBO
    2.Apply a gate voltage
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18
Q

The 3 conditions Required to gate “on” the SCR

A
  1. must be positive anode
  2. must be negative cathode
  3. gate must be positive compared to the cathode and have a 1.4 v knee voltage
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19
Q

The 4 conditions needed to turn off SCR

A
  1. install a switch on Anode
  2. Install shorting wire from anode to cathode
  3. put a negative signal on the gate
  4. drop holding current below L.C.D
20
Q

Condition Required to Turn on Triac

A

Negative on Terminal 1, Positive on Terminal 2, Positive on the gate with last least 1.5v potential to T1 and T2

21
Q

The condition required to turn off Triac

A

drop load current below holding current

22
Q

The Triac can be triggered into ______ in _____ direction by a gate ____ in either direction

A

conduction, either, current

23
Q

what could a Triac be replaced with

A

a mechanical cut-out switch

24
Q

A pair of Triacs and replace ______ contactors on a permanent ____ capacitor motor

A

reversing, split

25
Q

what instrument is used to make a rough test of a trial?

A

ohmmeter

26
Q

(TESTING)What should you see when the gate of Triac is open?

A

high ohms

27
Q

(TESTING)what should you see when the gate of the Triac is energized?

A

continuity

28
Q

What direction is a Diac

A

Bidirectional

29
Q

Does a Diac have a gate?

A

No

30
Q

Does a Triac have a gate?

A

Yes

31
Q

How does conduction initiate on Diac

A

when Voltage Break Out (VBO) is exceeded

32
Q

condition to turn off Diac

A

by dropping load current below holding current

33
Q

what does the Diac ensure the triac does not do?

A

ensures triac doesn’t turn on by spikes in the line

34
Q

How many layers in a Diac?

A

three layers

35
Q

Unlike the transistor, the junctions are _____ and _____ doped

A

heavily and equally

36
Q

Diacs are primarily used as a ______ device

A

Triggering

37
Q

When using an Ohmmeter to test a disc the resistance will be ______ when the disc is good

A

high in both directions

38
Q

Photo Cells are _______ devices

A

Light-Operated

39
Q

Photo Cells - when there is no light, resistance is _____

A

High

40
Q

Where are Photo Cells used

A

where time response is not critical

41
Q

what appliances are photoconductive cells often used on

A

large gas appliances

42
Q

Photo Diode is ____ operated

A

Light

43
Q

Photo Diode - No light means resistance is _____

A

High

44
Q

Photo Diode - operated in _______ bias mode

A

Reverse

45
Q

Do photo diodes exhibit fast or slow response time?

A

Fast

Level 4 : Electronics (6 decks)

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