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ECAD 2 Flashcards

1
Q

This circuit is a _____ oscillator.

(ECAD 2 yung hindi sa dulo ng discord)

A. Wien bridge
B. Hartley
C. phase-shift
D. Colpitts

A

D. Colpitts

It uses split capacitance (C1 and C2) in
the feedback.

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2
Q

What type of oscillator is shown in the
figure?

(ECAD 2 figure)

A. Wien
B. Phase-shift
C. Hartley
D. Colpitts

A

D. Colpitts

It uses split capacitance in the
feedback.

(ECAD 2 figure)

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3
Q

The sinusoidal oscillator is also called

A. Harmonic oscillator
B. LC oscillator
C. RC oscillator
D. Crystal oscillators

A

A. Harmonic oscillator

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4
Q

In order to start up, a feedback
oscillator requires

A. negative feedback less than 1
B. positive feedback greater than 1
C. no feedback
D. unity feedback equal to 1

A

B. positive feedback greater than 1

According to Barkhausen criterion:
A. to START Oscillation
1. Loop Gain (AB)>1
2. Phase Shift = 0 °,360 °, or any integer
multiple of 360°

B. to SUSTAIN Oscillation
1. Loop Gain (AB)=1
2. Phase Shift = 0°,360 °, or any integer
multiple of 360°

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5
Q

An oscillator differs from an amplifier
because the oscillator

A. requires no dc supply
B. requires no input signal
C. always has the same output
D. has more gain

A

B. requires no input signal

An oscillator don’t need an external input signal since it has a feedback circuit which is regenerative (positive feedback type) making it possible to generate output continuously ideally.

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6
Q

Refer to the given figure. This circuit is
known as

(ECAD 2 figure)

A. a Hartley oscillator
B. an Armstrong oscillator
C. a Clapp oscillator
D. a Colpitts oscillator

A

A. a Hartley oscillator

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7
Q

Which of the following is not an LC
oscillator

A. Hartley Oscillator
B. Clapp oscillator
C. Crystal oscillator
D. Colpitts oscillator

A

C. Crystal oscillator

Crystal oscillator is not an LC oscillator
because it does not contain any L or C.

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8
Q

The main feature of a crystal oscillator is

A. economy
B. high frequency
C. stability
D. reliability

A

C. stability

A crystal oscillator is an electronic
oscillator circuit that uses the
mechanical resonance of a vibrating
crystal of piezoelectric material to
create an electrical signal with a
constant frequency. One key advantage of this type of oscillator is its very high stability due to the high-Q characteristic of crystal components.

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9
Q

At series resonance, the impedance of a
crystal is

A. minimum
B. maximum
C. equal
D. zero

A

A. minimum

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10
Q

For sustaining oscillations in an
oscillator…

A. both feedback factor should be unity
and phase shift should be zero degrees
B. phase shift should be zero degrees
C. feedback should be negative
D. feedback factor should be unity

A

A. both feedback factor should be unity
and phase shift should be zero degrees

According to Barkhausen criterion:
A. to START Oscillation
1.Loop Gain (AB)>1
2. Phase Shift = 0 °, 360 °, or any integer
multiple of 360°

B. to SUSTAIN Oscillation
1. Loop Gain (AB)=1
2. Phase Shift = 0 °,360 °, or any integer
multiple of 360°

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11
Q

In practice, A is made _____
and the system is started oscillating by
amplifying noise voltage, which is
always present.

A. equal to 1
B. None of these choices
C. smaller than 1
D. greater than 1

A

D. greater than 1

According to Barkhausen criterion:
A. to START Oscillation
1.Loop Gain (AB)>1
2. Phase Shift = 0 °,360 °, or any integer
multiple of 360°

B. to SUSTAIN Oscillation
1.Loop Gain (AB)=1
2. Phase Shift = 0 °, 360 °, or any integer
multiple of 360°

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12
Q

The feedback signal in a(n) _____
oscillator is derived from an inductive
voltage divider in the LC circuit.

A. Hartley
B. Armstrong
C. None of these choices
D. Colpitts

A

A. Hartley

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13
Q

In pulses, fall time refers to the time
interval during which the output voltage(or current) falls from 90% to how many percent of the maximum value?

A. 0%
B. 5%
C. 10%
D. 50%

A

C. 10%

(ECAD 2 figure)

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14
Q

A second condition for oscillation is

A. no gain around the feedback loop
B. the attenuation of the feedback circuit
must be one-third
C. a gain of 1 around the feedback loop
D. the feedback circuit must be capacitive

A

C. a gain of 1 around the feedback loop

According to Barkhausen criterion:
A. to START Oscillation
1. Loop Gain (AB)>1
2. Phase Shift = 0 °,360 °, or any integer
multiple of 360°

B. to SUSTAIN Oscillation
1.Loop Gain (AB)=1
2. Phase Shift = 0°,360 °, or any integer
multiple of 360°

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15
Q

Which of the following is true regarding
Wien-bridge oscillators?
1. the frequency of oscillations can
easily be changed by using a
potentiometer
2. it can generate very high frequencies

A. neither 1 nor 2
B. 2 only
C. both 1 and 2
D. 1 only

A

D. 1 only

Wien-Bridge oscillator frequency of operation depends on the value of resistances and capacitances in the
lead-lag circuit. Using a variable resistor such as potentiometer in this part of the circuit will make it possible for the
frequency to be varied by adjusting the
resistance of the potentiometer. But,
since Wien-Bridge oscillator is an RC
oscillator, generally it is not good to use in generating very high frequencies. For very high frequencies it is better to use an LC type of oscillator.

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16
Q

In a Wien-bridge oscillator, if the
resistances in the positive feedback
circuit are decreased, the frequency

A. remains the same
B. increases
C. decreases
D. all of these choices

A

B. increases

(ECAD 2 album)

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17
Q

Refer to this figure. This circuit is

(ECAD 2 figure)

A. a sine-wave oscillator
B. an astablemultivibrator
C. a VCo
D. a monostablemultivibrator

A

B. an astablemultivibrator

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18
Q

Which of the following is not an LC
oscillator

A. Colpitts oscillator
B. Clapp oscillator
C. Hartley Oscillator
D. Crystal oscillator

A

D. Crystal oscillator

Crystal oscillator is not an LC oscillator
because it does not contain any L or C.

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19
Q

The sinusoidal oscillator is also called

A. LC oscillator
B. RC oscillator
C. Crystal oscillators
D. Harmonic oscillator

A

D. Harmonic oscillator

Sinusoidal oscillators are called
harmonic oscillators.

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20
Q

What is pin # 3 of an 8-pin 555 timer IC?

A. Discharge
B. Control
C. Output
D. Ground

A

C. Output

(ECAD 2 figure)

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21
Q

Which of the following is a circuit
consisting of a coil in parallel with a
capacitor?

A. feedback circuit
B. oscillator circuit
C. amplifier circuit
D. tank circuit

A

D. tank circuit

(ECAD 2 figure)

A tank circuit is a parallel
combination of a capacitor and
inductor and is the most common
“resonant” circuit –a circuit that
absorbs maximum power at a particular frequency (called the resonant frequency).

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22
Q

The _____ oscillator’s positive feedback
circuit is a lead-lag circuit.

A. Clapp
B. Wien-bridge
C. Phase-Shift
D. Armstrong

A

B. Wien-bridge

Wien-bridge oscillator uses a lead-lag
circuit (RC circuit) as the frequency
determining device and also as the
feedback network.

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23
Q

Which of the following oscillator cannot
be used in low frequency oscillations?

A. Wein bridge oscillators
B. RC oscillators
C. Colpitts oscillators
D. RC phase shift oscillators

A

C. Colpitts oscillators

Since Colpitts oscillator is an LC
oscillator it cannot be used as a low
frequency oscillator.

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24
Q

One phase shift network of an RC phase
contain _____ resistor

A. 0
B. 1
C. 3
D. 2

A

B. 1

One phase shift network of an RC phase
shift oscillator contains one capacitor
and one resistor.

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25
Q

Which of the following circuits is not a
relaxation oscillator?

A. multivibrator
B. sawtooth generator
C. pierce oscillator
D. blocking oscillator

A

C. pierce oscillator

Relaxation oscillators are non-
sinusoidal oscillators. Pierce oscillator
produces a sinusoidal waveform
therefore it does not belong to
relaxation oscillators

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26
Q

Which oscillator uses a tickler coil for
feedback?

A. Colpitts
B. Crystal
C. Armstrong
D. Hartley

A

C. Armstrong

Tickler coil or transformer is the feedback element of Armstrong oscillator.

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27
Q

One phase shift network of an RC phase
contain _____ inductor

A. 1
B. 0
C. 2
D. 3

A

B. 0

One phase shift network of an RC phase
shift oscillator contains one capacitor
and one resistor. There is no need of an
inductor.

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28
Q

Total phase shift provided by all phase
shift networks in RC phase shift
oscillator

A. 180 degrees
B. 120 degrees
C. 360 degrees
D. 60 degrees

A

A. 180 degrees

To satisfy Barkhausen’s criteria total
phase shift should be 360 degrees. 180
degrees is produced by amplifier and
rest by phase shift network even it is
three stage or four stage.

29
Q

In an 8 pin 555 timer IC, the supply
voltage must be connected in what pin #？

A. 6
B. 1
C. 8
D. 4

A

C. 8

30
Q

What is the difference between an
astable multivibrator and a monostable
multivibrator?

A. none of these choices
B. The monostable is free running
C. The astable needs to be clocked
D. The astable is free running

A

D. The astable is free running

31
Q

Phase shift provided by one phase shift network in RC phase shift oscillator in 3 stage is

A. 90 degrees
B. 180 degrees
C. 60 degrees
D. 120 degrees

A

C. 60 degrees

Phase shift provided by one phase shift oscillator in RC phase shift oscillator in 3 stage is 60 degrees. It is 180/number of stages.

32
Q

What type of MV is being shown in the
figure?

(ECAD 2 figure)

A. monostable
B. quasistable
C. astable
D. bistable

A

D. bistable

The coupling networks between the two
active components are both resistor,
therefore it is a bistable MV.

33
Q

Which component of Hartley oscillator
is used in feedback system?

A. Capacitor
B. Transistor
C. Resistor
D. Inductor

A

D. Inductor

Center tapped inductors are used in
Hartley oscillator to ensure feedback.

34
Q

What is pin # 7 of an 8-pin 555 timer IC?

A. Threshold
B. Discharge
C. Trigger
D. Ground

A

B. Discharge

35
Q

Hartley oscillator uses which type of
feedback

A. No feedback
B. Negative feedback
C. Positive feedback
D. Positive or Negative depends upon
frequency

A

C. Positive feedback

As normal oscillators Hartley oscillator
also uses positive feedback for
sustained oscillation.

36
Q

In the equivalent circuit of a crystal,which of the following represents the equivalent of the crystal when it is not vibrating?

A. mounting capacitance
B. dc resistance
C. null impedance
D. bulk inductance

A

A. mounting capacitance

37
Q

Which of the following is also known as
Eccless-Jordan circuit?

A. sawtooth generator
B. tuned oscillator
C. blocking oscillator
D. bistable multivibrator

A

D. bistable multivibrator

Bistable MV is also known as ECCLES-
JORDAN CIRCUIT or FLIP-FLOP CIRCUIT

38
Q

How many capacitors are there in the
tank circuit of Colpitts oscillator

A. 3
B. 1
C. 0
D. 2

A

D. 2

There are two capacitors in the tank circuit of Colpitts oscillator and it is given for voltage division.

39
Q

Which of the following oscillator is will
give most stable output oscillation
frequency?

A. Clapp oscillator
B. Colpitts oscillator
C. Wein bridge oscillator
D. Crystal oscillator

A

D. Crystal oscillator

Crystal oscillator gives the most stable
oscillation among sinusoidal oscillators.

40
Q

RC phase shift oscillators contains a
minimum of _____ Phase shift
network.

A. 3
B. 1
C. 0
D. 2

A

A. 3

RC phase shift oscillator contains a
minimum of three phase shift network.
There is can be also four and it
increases stability of oscillation.

41
Q

What is pin # 2 of an 8-pin 555 timer IC?

A. Ground
B. Threshold
C. Trigger
D. Discharge

A

C. Trigger

42
Q

Which of the following is another name
for a monostable MV?

A. free-running MV
B. one-shot MV
C. half-wave MV
D. absolute MV

A

B. one-shot MV

Monostable MV is also called ONE-
SHOT MV, SINGLE-SHOT MV, SINGLE-
SWING MV, DELAY MV, and
UNIVIBRATOR.

43
Q

What will be the phase shift of feedback
circuit in RC phase shift oscillator?

A. 180° phase shift
B. 60° phase shift
C. 90° phase shift
D. 360° phase shift

A

A. 180° phase shift

The RC feedback network provide 180°
phase shift and amplifier used in RC
phase shift oscillator provide 180°
phase shift (op-amp is used in the
inverting mode) to obtain a total phase
shift of 360°.

44
Q

This circuit is a _____ oscillator.

(ECAD 2 figure dulo ng discord)

A. Hartley
B. phase-shift
C. Wien bridge
D. Colpitts

A

B. phase-shift

Phase-shift oscillator is an RC oscillator
using RC ladder networks as the
feedback component and frequency
determining element. Typically, in this
type of oscillator three RC networks are
used.

45
Q

Which of the following parts of a pulse refers to the sum of the delay time and the rise time?

A. turn-on time
B. trigger time
C. turn-off time
D. pulse time

A

A. turn-on time

where,
Time Delay (td)
Rise Time (tr)
Turn-ON Time (Ton)
Storage Time (ts)
Fall Time (tf)
Turn-OFF Time (Toff)
Pulse Width (W)

Therefore,
Turn-on time = delay time + rise time
Turn-off time = storage time + fall time

46
Q

Which application best describes this
555 timer circuit?

(ECAD 2 figure)

A. Monostable multivibrator
B. Bistable multivibrator
C. Astable multivibrator
D. Free-running multivibrator

A

A. Monostable multivibrator

47
Q

Clapp oscillator is an

A. RC oscillator
B. LC oscillator
C. RL oscillator
D. Crystal oscillator

A

B. LC oscillator

Clapp oscillator is a colpitts oscillator
which has an extra capacitor series with
an inductor. Hence it is an LC oscillator.

48
Q

Which type of feedback is used in clapp
oscillator?

A. Positive feedback
B. Negative feedback
C. No feedback is used
D. Both positive and negative feedback

A

A. Positive feedback

Any oscillator circuit requires positive
feedback to ensure continuous
oscillations.

49
Q

Oscillators are used to _____ AC voltage.

A. Generate
B. Amplify
C. Rectify
D. Prevent

A

A. Generate

Oscillators are used for the generation
of AC voltage.

50
Q

An oscillator might fail to start for any
of the following reasons except:

A. In-phase feedback
B. Low-power-supply voltage
C. Low stage gain
D. Very low output impedance

A

A. In-phase feedback

Requirements to start oscillation:
1. Loop Gain (AB)>1
2. Phase Shift = 0 °, 360 °, or any integer
multiple of 360° à Positive or
Regenerative feedback

51
Q

What type of MV can be switched to the quasi-stable state by an external trigger pulse but it returns to the stable
condition after a time delay determined
by the value of circuit components?

A. quasistable
B. bistable
C. monostable
D. astable

A

C. monostable

52
Q

What is pin # 1 of an 8-pin 555 timer IC?

A. Discharge
B. Trigger
C. Threshold
D. Ground

A

D. Ground

53
Q

Which application best describes this
555 timer circuit? (ECAD 2 figure yung walang tanong pero may choices)

A. Astable multivibrator
B. Bistable multivibrator
C. One-shot multivibrator
D. Monostable multivibrator

A

A. Astable multivibrator

(ECAD 2 figure)

54
Q

Which of the following is not an
example for sinusoidal oscillator?

A. RC phase shift oscillator
B. Blocking oscillator
C. Crystal oscillator
D. Weinbridge oscillator

A

B. Blocking oscillator

A blocking oscillator is a waveform
generator that is used to produce
narrow pulses or trigger pulses. Since
the output of this circuit is not a
sinusoidal wave, it is not classified as a
sinusoidal oscillator.

55
Q

Which of the following is not an
example for non-sinusoidal oscillator

A. Multivibrator
B. Crystal oscillators
C. Sawtooth Generators
D. Blocking oscillators

A

B. Crystal oscillators

Since crystal oscillator produce a sine wave output it is not a non-sinusoidal oscillator.

56
Q

A multivibrator is an electronic circuit
used to implement

A. Timer
B. Flip-flop
C. Oscillator
D. All of these choices

A

D. All of these choices

A multivibrator is an electronic circuit used to implement a variety of simple two-state systems and two state
systems are oscillator, timer, flip-flop.

57
Q

How many types of multivibrators are
there?

A. 5
B. 3
C. 4
D. 2

A

B. 3

There are three types of multivibrator
circuits depending on the circuit
operation: (i) Astable, (i) Bistable, and
(ii) Monostable.

58
Q

What type of oscillator generates
waveforms that are not sinusoidal?

A. resonant
B. relaxation
C. vibration
D. harmonic

A

B. relaxation

Two general classification of oscillators:
Sinusoidal Oscillators - also known as
harmonic oscillators are those oscillator
circuits producing sinusoidal
waveforms.
Non-sinusoidal oscillators - also known
as relaxation oscillators are those
oscillator circuits producing non-
sinusoidal repetitive waveforms such as square, rectangular, sawtooth, triangular waveform etc.

59
Q

At parallel resonance, the impedance of
a crystal is

A. maximum
B. zero
C. equal
D. minimum

A

A. maximum

60
Q

One phase shift network of an RC phase
shift oscillator contain _____ capacitor

A. 0
B. 2
C. 1
D. 3

A

C. 1

One phase shift network of an RC phase
shift oscillator contains one capacitor
and one resistor.

61
Q

What is pin # 6 of an 8-pin 555 timer IC?

A. Threshold
B. Trigger
C. Discharge
D. Ground

A

A. Threshold

62
Q

In a typical IC monostable multivibrator circuit, at the falling edge of the trigger input, the output switches HIGH for a period of time determined by the

A. amplitude of the input trigger
B. magnitude of the dc supply voltage
C. value of the RC timing components
D. frequency of the input trigger

A

C. value of the RC timing components

63
Q

A 555 IC monostable timer has the
following number of stable states:

A. 1
B. 0
C. 3
D. 2

A

B. 0

64
Q

Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?

A. pulse stretching
B. Schmitt triggering
C. astable
D. monostable

A

C. astable

65
Q

Which of the following is not an I/0
terminal of a 555 timer IC?

A. Ground
B. Reset
C. Clock
D. Trigger

A

C. Clock

66
Q

Storage time refers to the time interval
between the end of the input pulse
(trailing edge) and the time when the output voltage (or current) falls to how many percent of its initial maximum value?

A. 100%
B. 10%
C. 0%
D. 90%

A

D. 90%

67
Q

Which type of multivibrator circuit is
also called delay multivibrator?

A. tristable
B. monostable
C. bistable
D. astable

A

B. monostable

Monostable MV is also called ONE-
SHOT MV, SINGLE-SHOT MV, SINGLE-
SWING MV, DELAY MV, and
UNIVIBRATOR.

68
Q

The frequency at which a crystal oscillator functions is determined mainly by:

A. The thickness of the crystal
B. The power-supply voltage
C. The amount of capacitance across the
crystal
D. The values of the biasing inductor and
capacitor

A

A. The thickness of the crystal

The natural resonant frequency of a
crystal depends on its cut. For a given crystal cut, the thinner the crystal, the higher the resonant frequency.

69
Q

In the internal circuit diagram of a 555 timer, the inverting input of the upper comparator is connected in what external terminal of the device?

A. reset
B. control voltage
C. trigger
D. discharge

A

B. control voltage

(ECAD 2 figure)

ELEX (13 decks)

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