Deck 2: Diodes and Applications

Question 1

A silicon diode measures a high value of resistance with the meter leads in both positions. The trouble, if any, is

A)the diode is internally shorted.
B)nothing; the diode is good.
C)the diode is open.
D)the diode is shorted to ground.

Answer 1

C

Question 2

The voltage regulation stage in a power supply

A)is inside the transformer.
B)is connected to the input of the rectifiers).
C)follows the filter stage.
D)is located preceding the transformer primary.

Answer 2

C

Question 3

Which of the circuits in Figure I will produce the signal in Figure II b)?

A)a)
B)b)
C)c)
D)d)

Answer 3

B

Question 4

A silicon diode is connected in series with a 10 k▲ resistor and a 12 V battery. If the cathode of the diode is connected to the positive terminal of the battery, the voltage from the anode to the negative terminal of the battery is

A)12 V.
B)0 V.
C)11.3 V.
D)0.7 V.

Question 5

The ripple frequency of a bridge rectifier is

A)one- half the input frequency.
B)four times the input frequency.
C)the same as the input frequency.
D)double the input frequency.

Question 6

A full- wave bridge rectifier uses _ diodes)in a bridge circuit.

A)3
B)1
C)2
D)4

Question 7

Figure I
Figure II
Refer to the figure above. This trace shows the output from

A)a full- wave rectifier with no filter and an open diode.
B)a half- wave rectifier with an open diode.
C)a half- wave rectifier with no filter.
D)a full- wave filtered rectifier with an open diode.

Question 8

A reverse- biased silicon diode is connected in series with a 12 V source and a resistor. The voltage across the diode is

A)0.3 V.
B)12 V.
C)0 V.
D)0.7 V.

Question 9

To reduce surge current, should be added to a power supply circuit.

A)a surge- limiting resistor
B)a larger fuse
C)additional filter capacitance
D)a varactor tuning circuit

Question 10

Figure I
Figure II
Refer to the figure above. This is the output from

A)a full- wave filtered rectifier with an open diode.
B)a half- wave rectifier with no filter.
C)a full- wave filtered rectifier.
D)a full- wave rectifier with no filter and an open diode.

Question 11

When a 60 Hz sinusoidal signal voltage is applied to the input of a half- wave rectifier, the output frequency is

A)30 Hz.
B)90 Hz.
C)120 Hz.
D)60 Hz.

Question 12

Figure I
Figure II
Which of the circuits in Figure I will produce the signal in Figure II c)?

A)a)
B)b)
C)c)
D)d)

Question 13

Figure I
Figure II
Which of the circuits in Figure I will produce the signal in Figure II a)?

A)a)
B)b)
C)c)
D)d)

Question 14

A typical value of reverse breakdown voltage in a diode is

A)0.3 V.
B)50 V or larger.
C)0.7 V.
D)0 V.

Question 15

The application of a dc voltage to control diode conduction is called

A)bias.
B)a pn junction.
C)oscillation.
D)amplification.

Question 16

Refer to the figure above. If the voltmeter across the transformer secondary reads 0 V, the probable trouble is that

A)the inductor is open.
B)one of the diodes is open.
C)the filter capacitor is open.
D)the transformer secondary is open.
E)No trouble exists; everything is normal.

Question 17

With a half- wave rectified voltage across a load resistor, load current exists for what part of a cycle?

A)180 degrees
B)0 degrees
C)90 degrees
D)360 degrees

Question 18

The diode in a half- wave rectifier conducts for of the input cycle.

A)180°
B)90°
C)45°
D)0°

Question 19

On diode check, a shorted diode will measure

A)0.7 V.
B)0.3 V.
C)0.79 V.
D)0 V.

Question 20

The knee voltage of a diode is approximately equal to the

A)applied voltage.
B)breakdown voltage.
C)reverse voltage.
D)barrier potential.

Question 21

Which of the circuits in Figure I will produce the signal in Figure II d)?

A)a)
B)b)
C)c)
D)d)

Question 22

The small current when a diode is reverse- biased is called

A)reverse- leakage current.
B)conventional current.
C)reverse breakdown current.
D)forward- bias current.

Question 23

If input frequency is 60 Hz, the output frequency of a bridge rectifier is

A)120 Hz.
B)30 Hz.
C)60 Hz.
D)240 Hz.

Question 24

A typical value of reverse breakdown voltage in a diode is

A)0.7 V.
B)0.3 V.
C)0 V.
D)50 V or larger.

Question 25

All of the following diode information is provided by a manufacturer's data sheet except

A)mechanical data.
B)temperature parameters.
C)frequency response.
D)PIV ratings.

Question 26

The ideal dc output voltage of a capacitor- input filter equals the

A)peak- to- peak value of the secondary voltage.
B)peak value of the rectified voltage.
C)average value of the rectified voltage.
D)rms value of the rectified voltage.

Question 27

A silicon diode has a voltage to ground of 117 V from the anode. The voltage to ground from the cathode is 117.7 V. The diode is

A)forward- biased.
B)shorted.
C)conducting.
D)reverse- biased.

Question 28

How much forward diode voltage is there with the ideal- diode approximation?

A)1 V
B)0.7 V
C)More than 0.7 V
D)0 V

Question 29

A diode clamper will

A)add an ac voltage to a signal.
B)eliminate the positive or negative alternation of a signal.
C)add a dc voltage to a signal.
D)clip off a portion of the input signal.

Question 30

Refer to the figure above. This oscilloscope trace indicates the output from

A)a full- wave filtered rectifier with an open diode.
B)a full- wave rectifier with no filter and an open diode.
C)a full- wave filtered rectifier.
D)a half- wave filtered rectifier.

Question 31

The resistance of a forward- biased diode is

A)infinite.
B)minimal below the knee of the curve.
C)minimal above the knee of the curve.
D)perfectly linear.

Question 32

Reverse bias is a condition that essentially current through the diode.

A)amplifies
B)prevents
C)allows
D)increases

Question 33

A diode is operated in reverse bias. As the reverse voltage is decreased, the depletion region

A)has a constant width.
B)is not related to reverse voltage.
C)narrows.
D)widens.

Question 34

A DMM measures 0.13 ▲ in both directions when testing a diode. The diode is

A)open.
B)operating normally.
C)shorted.
D)constructed of Si and is good.

Question 35

The forward voltage across a conducting silicon diode is about

A)0.7 V.
B)- 0.3 V.
C)1.3 V.
D)0.3 V.

Question 36

Using a practical forward- biased diode, if the voltage at the anode were 10 V, the voltage at the cathode would equal

A)10.3 V.
B)9.3 V.
C)10 V.
D)10.7 V.

Question 37

Voltage multipliers use action to increase peak rectified voltages without increasing the input transformer voltage rating.

A)clipping
B)cropping
C)charging
D)clamping

Question 38

A nonconducting diode is biased.

A)inverse
B)poorly
C)reverse
D)forward

Question 39

Refer to the figure above. The trace on this oscilloscope indicates the output from

A)a full- wave filtered rectifier with an open diode.
B)a half- wave rectifier with no filter.
C)a full- wave filtered rectifier.
D)a full- wave rectifier with no filter.

Question 40

A reverse- biased diode has the connected to the positive side of the source, and the connected towards the negative side of the source.

A)cathode, anode
B)base, anode
C)cathode, base
D)anode, cathode

Question 41

A filtered full- wave rectifier voltage has a smaller ripple than does a half- wave rectifier voltage for the same load resistance and capacitor values because

A)the larger the ripple, the better the filtering action.
B)of the longer time between peaks.
C)of the shorter time between peaks.
D)None of the above.

Question 42

A voltage regulator compensates for changes in

A)the input voltage.
B)the load conditions.
C)temperature.
D)All of the above.

Question 43

The peak inverse voltage across a nonconducting diode in an unfiltered bridge rectifier equals approximately

A)the peak value of the secondary voltage.
B)half the peak secondary voltage.
C)four times the peak value of the secondary voltage.
D)twice the peak secondary voltage.

Question 44

The dc current through each diode in a bridge rectifier equals

A)twice the dc load current.
B)half the dc load current.
C)one- fourth the dc load current.
D)the load current.

Question 45

What must be used in series with a forward- biased diode to prevent damage due to excessive current?

A)Nothing is required.
B)NC switch
C)Ammeter
D)Resistor

Question 46

Refer to the figure above. If the voltmeter across the transformer secondary reads 0 V, the probable trouble, if any, would be

A)the inductor is shorted.
B)the inductor is open.
C)one of the diodes is open.
D)an open transformer primary.

Question 47

If the positive lead of an ohmmeter is placed on the cathode and the negative lead is placed on the anode, which of the following readings would indicate a defective diode?

A)1 M▲
B)0 ▲
C)œ ▲
D)400 k▲

Question 48

Another name for a diode limiter is

A)bridger.
B)dc restorer.
C)clamper.
D)clipper.

Question 49

As the load resistance in a filtered power supply varies, the output voltage

A)remains constant.
B)is unaffected.
C)does not change.
D)varies.

Question 50

Refer to the figure above. These circuits are known as

A)clampers.
B)amplifiers.
C)clippers.
D)rectifiers.

Question 51

As the forward current through a forward- biased diode decreases, the voltage across the diode

A)immediately drops to 0 V.
B)increases.
C)increases and then decreases.
D)is relatively constant.

Question 52

The average value of the half- wave rectified output voltage is approximately of Vp.

A)31.8%
B)70.7%
C)63.6%
D)100%

Question 53

A reverse- biased silicon diode is connected in series with a 12 V source and a resistor. The voltage across the resistor is

A)0.7 V.
B)0 V.
C)0.3 V.
D)12 V.