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Level 4 : Electronics > Specials Diodes > Flashcards

Specials Diodes Flashcards

(45 cards)

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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

Study These Flashcards
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

Study These Flashcards
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

Study These Flashcards
A

drop load current below holding current

22
Q

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

Study These Flashcards
A

conduction, either, current

23
Q

what could a Triac be replaced with

Study These Flashcards
A

a mechanical cut-out switch

24
Q

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

Study These Flashcards
A

reversing, split

25
what instrument is used to make a rough test of a trial?
ohmmeter
26
(TESTING)What should you see when the gate of Triac is open?
high ohms
27
(TESTING)what should you see when the gate of the Triac is energized?
continuity
28
What direction is a Diac
Bidirectional
29
Does a Diac have a gate?
No
30
Does a Triac have a gate?
Yes
31
How does conduction initiate on Diac
when Voltage Break Out (VBO) is exceeded
32
condition to turn off Diac
by dropping load current below holding current
33
what does the Diac ensure the triac does not do?
ensures triac doesn't turn on by spikes in the line
34
How many layers in a Diac?
three layers
35
Unlike the transistor, the junctions are _____ and _____ doped
heavily and equally
36
Diacs are primarily used as a ______ device
Triggering
37
When using an Ohmmeter to test a disc the resistance will be ______ when the disc is good
high in both directions
38
Photo Cells are _______ devices
Light-Operated
39
Photo Cells - when there is no light, resistance is _____
High
40
Where are Photo Cells used
where time response is not critical
41
what appliances are photoconductive cells often used on
large gas appliances
42
Photo Diode is ____ operated
Light
43
Photo Diode - No light means resistance is _____
High
44
Photo Diode - operated in _______ bias mode
Reverse
45
Do photo diodes exhibit fast or slow response time?
Fast

Level 4 : Electronics (6 decks)

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