Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Elecs- Indiabix (Terms) > Electronic Devices 5- Voltage Reg to Thryristors > Flashcards

Electronic Devices 5- Voltage Reg to Thryristors Flashcards

(95 cards)

Start Studying
1
Q

The 7812 regulator IC provides ________.
5 V
–5 V
12 V
–12 V

A

12 V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Voltage regulators keep a constant ________ output voltage when the input or load varies within limits.
dc
ac
ripple

A

dc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In which period is the capacitor filter discharged through the load in a full-wave rectifier?
The time during the positive cycle
The time during which the diodes are not conducting
The time during which the diode(s) is (are) conducting
The time during the negative cycle

A

The time during which the diodes are not conducting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

The 7805 regulator IC provides ________.
5 V
–5 V
12 V
–12 V

A

5 V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the range of the voltage level of the LM317 adjusted voltage regulator?
0 V to 5 V
1.2 V to 37 V
–5 V to –24 V
5 V to 24 V

A

1.2 V to 37 V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Switching regulator efficiencies can be greater than ________ percent.
60
70
80
90

A

90

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The 7912 regulator IC provides ________ .
5 V
–5 V
12 V
–12 V

A

-12V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the typical dropout voltage for the 7812 fixed positive voltage regulator?
4 mV
100 mV
1.5 V
2 V

A

2V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the ratio of the period of the output voltage to the period of the input voltage in a full-wave rectifier?
0
0.5
1
2

A

0.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

If the value of full-load voltage is the same as the no-load voltage, the voltage regulation calculated is ________ %, which is the best expected.
0
1
99
100

A

0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

A switching regulator that is configured as a voltage-inverter produces what type of output?
an ac output with opposite phase to the input ac
a dc output that is the negative of the dc input voltage
an output that is a higher voltage than the input voltage
an ac output from a dc input voltage

A

a dc output that is the negative of the dc input voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the purpose of an additional RC filter section in a power supply circuit?
Increase the dc voltage component
Increase the ac voltage component
Decrease the ac voltage component
None of the above

A

Decrease the ac voltage component

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In which period is the capacitor filter charged in a full-wave rectifier?
The time during the positive cycle
The time during which the diodes are not conducting
The time during which the diode(s) is (are) conducting
The time during the negative cycle

A

The time during which the diode(s) is (are) conducting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The ________ regulator is less efficient than the ________ type, but offers inherent short-circuit protection.
series, shunt
shunt, series

A

shunt, series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In which of the following applications is a pulsating dc voltage suitable?
Battery charger
Radio
Stereo system
Computer

A

Battery charger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In a series regulator, what is the purpose of fold-back limiting?
to provide more current in the case of a short circuit
to limit output voltage if input voltage goes too high
to bypass the pass-transistor, if the pass-transistor should fail
to provide current up to a maximum, but drop current to a lower value when the output becomes shorted, to prevent overheating of the device

A

to provide current up to a maximum, but drop current to a lower value when the output becomes shorted, to prevent overheating of the device

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In a simple series regulator circuit, which of the following components is the controlling element?
Load resistor
Zener diode
Transistor Q1
None of the abov

A

Transistor Q1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

In an improved shunt regulator, which of the following components sets the reference voltage?
Transistor Q1
Zener diode
Transistor Q2
RS

A

Zener diode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

________ regulation can be defined as the percentage change in the output voltage for a given change in load current.
Line
Load

A

Load

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How many diodes conduct in the full-wave bridge rectifier while the capacitor is being charged?
1
2
3
4

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How many terminals does a 7800 series IC regulator have?
2
3
4
none of the above

A

3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the typical values of Vref and Iadj for the LM317 adjustable voltage regulator?
1.0 V, 100 mA
1.5 V, 100 mA
1.25 V, 100 μA
1.25 V, 10 mA

A

1.25 V, 100 μA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Which component(s) set(s) the voltage across the load in a basic transistor shunt regulator?
Zener diode
Transistor base-emitter voltage
Both the Zener diode and the transistor base-emitter voltage
None of the above

A

Both the Zener diode and the transistor base-emitter voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Voltage regulation requires
only line regulation.
only load regulation.
a constant load.
load and line regulation.

A

load and line regulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Across which of the following components of a power supply does the average (dc) voltage exist? Diodes Secondary of the transformer Capacitor filter None of the above
Capacitor filter
26
Switching regulators are more efficient than linear regulators and are particularly useful in ________-voltage, ________-current applications. high, high low, high high, low
low, high
27
For what range of load current can voltage regulators be selected for operation? Hundreds of picoamperes to tens of nanoamperes Hundreds of picoamperes to tens of milliamperes Hundreds of milliamperes to tens of amperes None of the above
Hundreds of milliamperes to tens of amperes
28
The 7905 regulator IC provides ________. 5 V –5 V 12 V –12 V
-5V
29
What type of regulator offers inherent short-circuit protection? shunt regulators series regulators three-terminal regulators switching regulators
shunt regulators
30
In a shunt linear regulator, the control element is a(n) ________ in parallel with the load. inductor capacitor transistor
Transistor
31
For what range of fixed regulated voltages do the series 78xx regulators provide regulation? +5 V to +24 V +5 V to +24 V –5 V to –24 V None of the above
+5 V to +24 V
32
In a series linear regulator, the control element is a(n) ________ in series with the load. inductor capacitor transistor
transistor
33
________ regulation can be defined as the percentage change in the output voltage for a given change in the input voltage. Line Load
Line
34
A ________ -wave rectified signal has less ripple than a ________ -wave rectified signal and is thus better to apply to a filter. full, half half, full
full, half
35
Only the condition betaA = ________ must be satisfied for self-sustained oscillations to result. 0 –1 1 None of the above
1
36
At what phase shift is the magnitude of betaA at its maximum in the Nyquist plot? 90º 180º 270º 0º
180º
37
Which of the following improvements is (are) a result of the negative feedback in a circuit? Lower output impedance Reduced noise More linear operation All of the above
All of the above
38
The feedback signal in a(n) ________ oscillator is derived from an inductive voltage divider in the LC circuit. Hartley Armstrong Colpitts
Hartley
39
The attenuation of the three-section RC feedback phase-shift oscillator is 1/9. 1/30. 1/3. 1/29.
1/29
40
For a phase-shift oscillator, the gain of the amplifier stage must be greater than ________. 19 29 30 1
29
41
Which of the following is (are) the determining factor(s) of the stability of a feedback amplifier? A Phase shift between input and output signals Both A and the phase shift between input and output signals None of the above
Both A and the phase shift between input and output signals
42
What is the minimum frequency at which a crystal will oscillate? seventh harmonic third harmonic fundamental second harmonic
fundamental
43
The feedback signal in a(n) ________ oscillator is derived from a capacitive voltage divider in the LC circuit. Hartley Armstrong Colpitts
Colpitts
44
Sinusoidal oscillators operate with ________ feedback. positive negative
positive
45
Which of the following is required for oscillation? betaA > 1 The phase shift around the feedback network must be 180º. Both betaA > 1 and the phase shift around the feedback network must be 180º. None of the above
Both betaA > 1 and the phase shift around the feedback network must be 180º.
46
A circuit that can change the frequency of oscillation with an application of a dc voltage is sometimes called a voltage-controlled oscillator. a crystal oscillator. a Hartley oscillator. an astable multivibrator.
a voltage-controlled oscillator.
47
In order to start up, a feedback oscillator requires negative feedback less than 1. positive feedback greater than 1. unity feedback equal to 1. no feedback.
positive feedback greater than 1.
48
What is the ratio of the input impedance with series feedback to that without feedback? 1 + betaA betaA beta 1
1+betaA
49
Which of the following oscillators is (are) tuned oscillators? Colpitts Hartley Crystal All of the above
All of the above
50
What is the ratio of the output impedance with series feedback to that without feedback? 1 1 + betaA betaA A
1+betaA
51
One condition for positive feedback is that the phase shift around the feedback loop must be ________°. 0 90 180 45
0
52
At what phase shift is the magnitude of A at its minimum in the Nyquist plot? 90º 180º 270º 0º
0
53
What is the total phase shift requirement, around the feedback loop, for a phase-shift oscillator? 90° 180° 270° 360°
360
54
The lead-lag circuit in the Wien-bridge oscillator has a resonant frequency at which the attenuation is 1/2. 1/4. 1/3. 1/5.
1/3
55
The start-up gain of an oscillator must be ________ one. equal to less than greater than
greater than
56
In the IC phase-shift oscillator, what should the ratio of feedback resistor Rf to R1 be? Zero Greater than –29 Less than 29 Any value
greater than -29
57
At series resonance, the impedance of a crystal is minimum. maximum. equal. zero.
minimum
58
For frequencies up to 1 MHz, the ________ is the most widely used type of sinusoidal RC oscillator. Wien-bridge phase-shift twin-T
Wien-bridge
59
The twin-T oscillator produces a ________ response. low-pass high-pass band-pass band-stop
bandstop
60
What is the typical value of quality factor for crystal oscillators? 20,000 1000 100 10
20,000
61
Which of the following improvements is (are) a result of the negative feedback in a circuit? Higher input impedance Better stabilized voltage gain Improved frequency response All of the above
All of the above
62
In the Wien bridge oscillator, which of the following is (are) frequency-determining components? R1 and R2 C1 and C2 R1, R2, C1, and C2 None of the above
R1, R2, C1, and C2
63
A certain oscillator has a tap on the inductor in the tank circuit. This oscillator is probably a Colpitts oscillator. a Clapp oscillator. a crystal oscillator. a Hartley oscillator.
a Hartley oscillator.
64
At parallel resonance, the impedance of a crystal is minimum. maximum. equal. zero.
maximum
65
Which of the following is (are) feedback? Voltage-series Voltage-shunt Current-series All of the above
All of the above
66
What is the relationship between the series and parallel resonant frequencies of a quartz crystal? They are equal. Parallel resonant frequency is approximately 1 kHz higher than series resonant frequency. Series resonant frequency is approximately 1 kHz higher than parallel resonant frequency. none of the above
Parallel resonant frequency is approximately 1 kHz higher than series resonant frequency.
67
An op-amp integrator has a square-wave input. The output should be a sine wave. a triangle wave. a square wave. pure dc.
a triangle wave
68
A ________ filter rejects all frequencies within a specified band and passes all those outside this band. low-pass high-pass band-pass band-stop
band-stop
69
Filters with the ________ characteristic are useful when a rapid roll-off is required because it provides a roll-off rate greater than –20/dB/decade/pole. Butterworth Chebyshev Bessel
Chebyshev
70
A ________ filter significantly attenuates all frequencies below fc and passes all frequencies above fc. low-pass high-pass band-pass band-stop
high-pass
71
The bandwidth in a ________ filter equals the critical frequency. low-pass high-pass band-pass band-stop
low-pass
72
Filters with the ________ characteristic are used for filtering pulse waveforms. Butterworth Chebyshev Bessel
Bessel
73
Which filter exhibits a linear phase characteristic? Bessel Butterworth Chebyshev all of the above
Bessel
74
The critical frequency is defined as the point at which the response drops ________ from the passband. –20 dB –3 dB –6 dB –40 dB
–3 dB
75
Filters with the ________ characteristic provide a very flat amplitude in the passband and a roll-off rate of –20 dB/decade/pole. Butterworth Chebyshev Bessel
Butterworth
76
Which filter exhibits the most rapid roll-off rate? Bessel Butterworth Chebyshev all of the above
Chebyshev
77
Which filter has a maximally flat response? Bessel Butterworth Chebyshev all of the above
Butterworth
78
One important application of a state-variable ________ filter with a summing amplifier is to minimize the 60 Hz "hum" in audio systems. low-pass high-pass band-pass band-stop
band-stop
79
A third-order filter will have a roll-off rate of –20 dB/decade. –40 dB/decade. –60 dB/decade. –30 dB/decade.
–60 dB/decade.
80
A ________ filter passes all frequencies within a band between a lower and an upper critical frequency and rejects all others outside this band. low-pass high-pass band-pass band-stop
band-pass
81
The ________ can be externally programmed to turn on at a desired anode-to-gate voltage level. UJT PUT SCR SCS
PUT
82
You need a very efficient thyristor to control the speed of an AC fan motor. A good device to use would be a 4-layer diode. a PUT. a triac. a BJT.
a triac
83
An application of a(n) ________ is in a lighting system for power interruptions. SCR SCS diac triac
SCR
84
The silicon-controlled switch (SCS) is similar in construction to the triac. diac. SCR. 4-layer diode.
SCR.
85
The ________ can conduct current in either direction and is turned on when a breakover voltage is exceeded. SCR diac SCS triac
diac
86
You need to design a relaxation oscillator circuit. The most likely device to use might be an SCR. a UJT. a triac. a 4-layer diode.
a UJT
87
You have the schematic diagram of several types of circuits. Which of these circuits most likely uses a triac? an oscillator an ac motor control a programmable oscillator an amplifier
an ac motor control
88
The ________ is like a diac with a gate terminal. triac SCR SCS none of the above
triac
89
You have a need to use a device to trigger an SCR. A good one to use might be an SCS. a UJT. a 4-layer diode. a PUT.
a UJT.
90
The SCR can be triggered on by a pulse at the gate. anode. cathode. none of the above
gate.
91
Which of the following devices might best be used to control an electric motor? an SCS a PUT an SCR a diac
an SCR
92
You have a light-dimmer circuit using an SCR. In testing the circuit, you find that IG = 0 mA and the light is still on. You conclude that the trouble might be one of the following: the SCR is open. the switch is faulty. the gate circuit is shorted. this is normal; nothing is wrong.
this is normal; nothing is wrong.
93
How many semiconductor layers are thyristors constructed with? 2 3 4 5
4
94
Your boss has asked you to recommend a thyristor that will enable you to turn it on with a pulse and also turn it off with a pulse. Which of the following should you recommend? an SCR an SCS a PUT a triac
an SCS
95
An SCR acts to control the speed of an electric motor by ________ the ________ of the pulse delivered to the motor. varying, width increasing, amplitude decreasing, gate width none of these
varying, width

Elecs- Indiabix (Terms) (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions