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neets 7 > CH 3 > Flashcards

CH 3 Flashcards

1
Q

In a reverse biased PN-junction, which current carriers cause leakage current?

A

The minority carriers

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2
Q

The action of a PN-junction during breakdown can be explained by what two theories?

A

Zener effect and avalanche effect

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3
Q

Which breakdown theory explains the action that takes place in a heavily doped PN-junction with a reverse bias of less than 5 volts?

A

Zener effect

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4
Q

What is the doping level of an avalanche effect diode when compared to the doping level of a Zener-effect diode?

A

The doping level of an avalanche effect diode is lower

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5
Q

During avalanche effect breakdown, what limits current flow through the diode?

A

An external current-limiting resistor.

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6
Q

Why is electron flow with the arrow in the symbol of a Zener diode instead of against the arrow as it is in a normal diode?

A

Because Zener diodes are operated in the reverse bias mode.

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7
Q

What is the main difference in construction between normal PN junction diodes and tunnel diodes?

A

The amount of doping.

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8
Q

What resistance property is found in tunnel diodes but not in normal diodes?

A

Negative resistance.

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9
Q

When compared to the ordinary diode, the tunnel diode has what type of depletion region?

A

The tunnel diode has a very narrow depletion region

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10
Q

In the tunnel diode, the tunneling current is at what level when the forbidden gap of the N-type material is at the same energy level as the empty states of the P-type material?

A

Minimum.

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11
Q

The varactor displays what useful electrical property?

A

Variable capacitance

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12
Q

When a PN junction is forward biased, what happens to the depletion region?

A

The depletion region decreases.

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13
Q

When the reverse bias on a varactor is increased, what happens to the effective capacitance?

A

Capacitance decreases.

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14
Q

The SCR is primarily used for what function?

A

The SCR is primarily used for switching power on or off.

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15
Q

When an SCR is forward biased, what is needed to cause it to conduct?

A

A gate signal.

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16
Q

What is the only way to cause an SCR to stop conducting?

A

The forward bias must be reduced below the minimum conduction level.

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17
Q

The TRIAC is similar in operation to what device?

A

SCR.

18
Q

When used for ac current control, during which alternation of the ac cycle does the TRIAC control current flow?

A

During both alternations.

19
Q

What type of bias is required to cause an LED to produce light?

A

Forward bias

20
Q

When compared to incandescent lamps, what is the power requirement of an LED?

A

Very low

21
Q

In a common anode, seven-segment LED display, an individual LED will light if a negative voltage is applied to what element?

A

The cathode.

22
Q

What is the resistance level of a photodiode in total darkness?

A

Very high

23
Q

What type of bias is required for proper operation of a photodiode?

A

Reverse bias

24
Q

What is a typical light-to-dark resistance ratio for a photocell?

A

1:1000.

25
Q

What semiconductor device produces electrical energy when exposed to light?

A

Photovoltaic cell.

26
Q

The UJT has how many PN junctions?

A

One

27
Q

The area between base 1 and base 2 in a UJT acts as what type of common circuit component?

A

Variable resistor.

28
Q

The sequential rise in voltage between the two bases of the UJT is called what?

A

A voltage gradient.

29
Q

What is the normal current path for a UJT?

A

From base 1 to the emitter.

30
Q

What is one of the primary advantages of the FET when compared to the bipolar transistor?

A

High input impedance.

31
Q

The FET and the vacuum tube have what in common?

A

Voltage controls conduction.

32
Q

The base of a transistor serves a purpose similar to what element of the FET?

A

Gate.

33
Q

Q33. What are the two types of JFET?

A

N-channel and P-channel.

34
Q

The source and drain of an N-channel JFET are made of what type of material?

A

N-type material.

35
Q

What is the key to FET operation?

A

Effective cross-sectional area of the channel.

36
Q

What is the normal current path in an N-channel JFET?

A

From source to drain.

37
Q

Applying a reverse bias to the gate of an FET has what effect?

A

Source-to-drain resistance increases.

38
Q

The input and output signals of a JFET amplifier have what phase relationship?

A

They are 180 degrees out of phase.

39
Q

When compared to the JFET, what is the input impedance of the MOSFET?

A

The MOSFET has a higher input impedance.

40
Q

What are the four elements of the MOSFET?

A

Gate, source, drain, and substrate.

41
Q

The substrate of an N-channel MOSFET is made of what material?

A

P-type material.

42
Q

In a MOSFET, which element is insulated from the channel material?

A

The gate terminal.

neets 7 (3 decks)

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