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Electronics 3 > Silicon Controlled Rectifier > Flashcards

Silicon Controlled Rectifier Flashcards

1
Q

What is an SCR?

A

Silicon Controlled Rectifier

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2
Q

The name “silicon controlled rectifier” is General Electric’s trade name for a type of ______.

A

Thyristor

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3
Q

SCRs are mainly used in electronic devices that reqire control of ____ voltage and power.

A

High

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4
Q

How many layers of semiconductors does an SCR have?

A

4 layers

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5
Q

Two structures formed within the SCR.

A

NPNP and PNPN

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6
Q

What are the junctions of an SCR?

A

J1, J2, and J3

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7
Q

What are the terminals of an SCR?

A

Anode, Cathode, Gate

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8
Q

What are the modes of operation for an SCR depending upon biasing?

A

Forward Blocking Mode
Forward Conduction Mode
Reverse Blocking Mode

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9
Q

Happens when anode is positive with respect to cathode and gate terminal is open.

A

Forward Blocking Mode

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10
Q

What junction can’t current pass through in forward bias, forward blocking mode?

A

J2

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11
Q

Two ways to bring SCR from blocking to conduction mode.

A

Increasing voltage between anode and cathode beyond the breakover voltage

Applying a positive pulse at the gate

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12
Q

The gate voltage required to maintain an SCR in the ON state.

A

0

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13
Q

The minimum current necessary to maintain SCR in the ON state.

A

Latching Current

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14
Q

A thyristor is brought from forward blocking mode to forward conducting mode by applying required ______.

A

Gate Voltage

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15
Q

Happens when negative voltage is applied to the anode and positive voltage to the cathode.

A

Reverse Blocking Mode

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16
Q

If forward voltage is increase in forward blocking mode, what happens to the J2 junction?

A

Avalanche Breakdown

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17
Q

An SCR incapable of blocking reverse voltage.

A

Asymmetrical SCR or ASCR

18
Q

Typical reverse breakdown rating of an ASCR

A

Tens of Volts

19
Q

Reverse conducting diodes used to fabricate ASCRs

A

RCT or reverse conducting thyristor

20
Q

Thyristor Turn On Methods

A

Forward-Voltage Triggering
Gate Triggering
Dv/Dt Triggering
Temperature Triggering
Light Triggering

21
Q

Occurs when the anode-cathode forward voltage is increased with the gate circuit opened.

A

Forward-voltage triggering

22
Q

Occurs when the thyristor should be in forward blocking state where the applied voltage is less than the breakdown voltage.

A

Gate Triggering

23
Q

Occurs when the width of depletion region decreases as the temperature is increased

A

Temperature Triggering

24
Q

During a rudimentary test of SCR, where do you put the red test lead?

A

Gate

25
Q

During a rudimentary test of SCR, where do you put the black test lead?

A

Cathode

26
Q

What should the ohmmeter show when doing a rudimentary test of SCR?

A

Continuity/OL

27
Q

“Normal” SCRs that are lacking an internal resistors are sometimes referred to as _____.

A

Sensitive Gate SCRs

28
Q

A circuit that consists of an SCR placed in parallel with the output of a DC power supply, for placing a direct short-circuit on the output of that supply to prevent excessive voltage from reaching the load.

A

Crowbar

29
Q

The electron tube version of an SCR

A

Thyratron

30
Q

An SCR that is specifically designed to be turned off by means of reverse triggering.

A

Gate-Turn-Off Thyristor (GTO)

31
Q

Thyristors are mainly used in devices where the control of ____ power, possibly coupled with ____ voltage is demanded.

A

high, high

32
Q

It is the minimum forward voltage, gate being open, at which SCR starts conducting heavily.

A

Breakover Voltage

33
Q

Commercially available SCRs have what range of breakover voltages?

A

50V to 500V

34
Q

It is the maximum reverse voltage that can be applied to an SCR without conducting in the reverse direction.

A

Peak Reverse Voltage

35
Q

It is the maximum anode current, gate being open, at which SCR is turned off from ON conditions.

A

Holding Current

35
Q

Commercially available SCRs have PRV ratings up to ___.

A

2.5kV

36
Q

It is the maximum anode current that an SCR is capable of passing without destruction.

A

Forward Current Rating

37
Q

Commercially available SCRs have forward current ratings of ___.

A

30A to 100A

38
Q

Indicates the maximum forward surge current capability of SCR.

A

Circuit Fusing Rating

39
Q

The ____ the firing angle, the ____ is the average current.

A

greater, smaller

Electronics 3 (7 decks)

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