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UNIT III

Total questions: 75

Worksheet time: 38mins

Name
Class
Date
1.

Oscillators are used to ______ AC voltage.

a)

Prevent

b)

Generate

c)

Amplify

d)

Rectify

2.

Oscillator __________ an AC input for giving an AC output.

a)

Doesn’t need

b)

Need

c)

Doesn’t need at lower frequencies

d)

Doesn’t need at higher frequencies

3.

Negative resistance are incorporated in oscillator for ___________

a)

Sustained oscillation

b)

Damped oscillation

c)

Biasing the oscillator

d)

Increasing amplitude of oscillation

4.

The output of oscillator will not depend upon ___________

a)

Feedback

b)

Amplifier

c)

Input voltage

d)

Both feedback and amplifier

5.

In an oscillator if phase of feedback is same as that of oscillation waveform then feedback is called ___________

a)

Positive feedback

b)

Negative feedback

c)

Cannot be predicted

d)

Either positive or negative depending upon frequency

6.

The output waveform of a stable oscillator have ___________

a)

Constant frequency at low amplitude only

b)

Constant frequency at high amplitude only

c)

Variable frequency

d)

Constant frequency

7.

The output of a stable oscillator have ___________

a)

Constant amplitude

b)

Varying amplitude

c)

Constant amplitude at high frequencies only

d)

Constant amplitude at low frequencies only

8.

The AC power of output signal is obtained by ___________

a)

Input AC voltage

b)

Input DC voltage

c)

DC biasing voltage

d)

Power is generated by transistor itself

9.

. Primary trigger for oscillation is obtained from ___________

a)

DC voltage

b)

Noise voltage

c)

External trigger voltage

d)

No trigger is required

10.

Phase shift provided by overall tank circuit is ___________

a)

0 degree

b)

90 degree

c)

180 degree

d)

-90 degree

11.

Which configuration of the transistor amplifier is used for Hartley oscillator?

a)

Common emitter amplifier

b)

Common collector amplifier

c)

Common base amplifier

d)

Combination of both common emitter and common collector

12.

RC phase shift oscillators contain a minimum of _________ Phase shift network.

a)

1

b)

2

c)

3

d)

0

13.

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

a)

180 degrees

b)

60 degrees

c)

120 degrees

d)

90 degrees

14.

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

a)

180 degrees

b)

60 degrees

c)

120 degrees

d)

360 degree

15.

Amplifier gain for RC phase shift oscillation, to obey Barkhausen’s criteria should be minimum of ___________

a)

43

b)

4

c)

10

d)

29

16.

Frequency of oscillation for three section RC phase shift network is given by ___________

a)

1/(ᴨ√6 RC)

b)

2/(ᴨ√6 RC)

c)

1/(2ᴨ√6 RC)

d)

1/(2√6 RC)

17.

FET is a voltage controlled device.

a)

a) True

b)

b) False

18.

Which of the following statement is true about FET?

a)

a) It has high output impedance

b)

b) It has high input impedance

c)

c) It has low input impedance

d)

d) It does not offer any resistance

19.

Comparing the size of BJT and FET, choose the correct statement?

a)

a) BJT is larger than the FET

b)

b) BJT is smaller than the FET

c)

c) Both are of same size

d)

d) Depends on application

20.

For a FET when will maximum current flows?

a)

a) Vgs = 0V

b)

b) Vgs = 0v and Vds >= |Vp|

c)

c) VDS >= |Vp|

d)

d) Vp = 0

21.

What is the value of current when the gate to source voltage is less than the pinch off voltage?

a)

a) 1A

b)

b) 5A

c)

c) 100A

d)

d) 0

22.

What is the value of drain current when Vgs=pinch off voltage?

a)

a) 0A

b)

b) 1A

c)

c) 2A

d)

d) Cannot be determined

23.

For an n-channel FET, What is the direction of current flow?

a)

a) Source to drain

b)

b) Drain to source

c)

c) Gate to source

d)

d) Gate to drain

24.

How does a FET behave when the v-I characteristics are to the left of pinch off for an n channel FET?

a)

a) Voltage controlled resistor

b)

b) Amplifier

c)

c) Switch

d)

d) Diode

25.

Where does the transfer curve lie for a p- channel FET?

a)

a) First quadrant

b)

b) Second quadrant

c)

c) Third quadrant

d)

d) Fourth quadrant

26.

JFET is a ______ carrier device.

a)

a) Unipolar

b)

b) Bipolar

c)

c) Minority

d)

d) Majority

27.

The n-channel JFET, the pinch off voltage is ______________

a)

a) not greater than 0

b)

b) greater than or equal to 0

c)

c) less than or equal to 0

d)

d) not less than 0

28.

Which of these has an output which follows input?

a)

a) CS amplifier with a bypass capacitor

b)

b) CD amplifier

c)

c) CG amplifier

d)

d) CS amplifier without a bypass capacitor

29.

How many terminals are there in a unijunction transistor?

a)

a) 1

b)

b) 2

c)

c) 3

d)

d) 4

30.

What are unijunction transistors used for?

a)

a) Amplifying a circuit

b)

b) Circuit breaker

c)

c) Splitting device

d)

d) On-Off switching device

31.

What is the intrinsic stand-off ratio(η) of a unijunction transistor when RB1 = 10kΩ and RBB = 15kΩ?

a)

a) 0.67

b)

b) 0.55

c)

c) 0.80

d)

d) 0.44

32.

What is the generalized value for the voltage across resistor RB1 in a unijunction transistor?

a)

a) VRB1 = (RB2 / RB1 + RB2) × VBB

b)

b) VRB1 = (RB2 / RB1 – RB2) × VBB

c)

c) VRB1 = (RB1 / RB1 + RB2) × VBB

d)

d) VRB1 = (RB1 / RB1 – RB2) × VBB

33.

Unijunction transistors have unidirectional conductivity and positive resistance characteristics.

a)

a) True

b)

b) False

34.

Which type of material is the channel of a unijunction transistor made up of?

a)

a) PN type

b)

b) P type

c)

c) N type

35.

What are the terminals of a unijunction transistor?

a)

a) Collector, Base and Emitter

b)

b) Emitter, Base 1 and Base 2

c)

c) Gate, Drain and Source

d)

d) Gate, Base 1 and Base 2

36.

What are the working regions of a unijunction transistor?

a)

a) Linear region

b)

b) Negative Resistance region

c)

c) Saturation region

d)

d) Cut-off region

37.

What are unijunction transistors used for?

a)

a) Amplifying a circuit

b)

b) Circuit breaker

c)

d) On-Off switching device

d)

c) Splitting device

38.

P side emitter in UJT is

a)

not doped

b)

feebly doped

c)

heavily doped

d)

moderately doped

39.

In UJT relaxation Oscillator ,the value of RBB is 5 K ohms, intrinsic stand off ratio is 0.6.Find the value of RB2

a)

3 K ohms

b)

5 K ohms

c)

2 K ohms

d)

4 K ohms

40.

After peak point UJT operates in -------------------- region

a)

cut off

b)

saturation

c)

negative resistance

d)

pinch off

41.

UJT is sometimes called as --------------------- diode

a)

Low resistance

b)

High resistance

c)

single base

d)

double base

42.

When the temperature increases ,the value of intrinsic stand off ratio

a)

increases

b)

decreases

c)

remains the same

43.

When UJT is turned on , the resistance between Emitter terminal and Base 1 terminal

a)

remains the same

b)

is decreased

c)

is increased

44.

Operation of relaxation Oscillator is based on charging and discharging of

a)

inductor

b)

resistor

c)

capacitor

45.

----------------- criterion determines the condition to obtain sustained oscillations

a)

Pythagorous

b)

Norton

c)

Barkhausen

46.

UJT is used in ------------------------- oscillator

a)

Colpitts

b)

Hartley

c)

crystal

d)

relaxation

47.

Which is the most stable oscillator ?

a)

Colpitts

b)

Hartley

c)

RC Phase Shift

d)

Crystal

48.

Basic difference between oscillator and amplifier is ------

a)

high gain

b)

no input signal is needed

c)

frequency stability

49.

The gate of a JFET is ………… biased

a)

reverse

b)

forward

c)

reverse as well as forward

50.

In a p-channel JFET, the charge carriers are …………..

a)

electrons

b)

holes

c)

both electrons and holes

51.

When drain voltage equals the pinch-off-voltage, then drain current …………. with the increase in drain voltage

a)

decreases

b)

increases

c)

remains constant

52.

If the reverse bias on the gate of a JFET is increased, then width of the conducting channel --------------------------

a)

is decreased

b)

is increased

c)

remains the same

53.

The input control parameter of a JFET is ……………

a)

gate voltage

b)

source voltage

c)

drain voltage

d)

gate current

54.

A JFET has high input impedance because …………

a)

it is made of semiconductor material

b)

input is reverse biased

c)

of impurity atoms

55.

In a JFET, IDSS is known as …………..

a)

drain to source current

b)

drain to source current with gate shorted

c)

drain to source current with gate open

56.

The two important advantages of a JFET are …………..

a)

high input impedance and square-law property

b)

inexpensive and high output impedance

c)

low input impedance and high output impedance

57.

The gate voltage in a JFET at which drain current becomes zero is called ……….. voltage

a)

saturation

b)

pinch-off

c)

active

d)

cut-off

58.

In a FET, there are ……….. pn junctions at the sides

a)

three

b)

four

c)

five

d)

two

59.

The channel of a JFET is between the …………….

a)

gate and drain

b)

drain and source

c)

gate and source

d)

input and output

60.

For VGS = 0 V, the drain current becomes constant when VDS exceeds ………

a)

cut off

b)

VDD

c)

VP

d)

0 V

61.

At cut-off, the JFET channel is ……….

a)

at its widest point

b)

completely closed by the depletion region

c)

extremely narrow

d)

reverse baised

62.

In a common-source JFET amplifier, the output voltage is …………………

a)

180o out of phase with the input

b)

in phase with the input

c)

90o out of phase with the input

d)

taken at the source

63.

A JFET is a ………… driven device

a)

current

b)

voltage

c)

both current and voltage

64.

A JFET is also called …………… transistor

a)

unipolar

b)

bipolar

c)

unijunction

65.

Hartley oscillator consists of ________ inductors.

a)

1

b)

2

c)

3

d)

4

66.

Colpitts oscillator consists of ________ inductors.

a)

1

b)

2

c)

3

d)

4

67.

Hartley oscillator consists of ________ capacitors.

a)

1

b)

2

c)

3

d)

4

68.

Colpitts oscillator consists of ________ capacitors.

a)

1

b)

2

c)

3

d)

4

69.

Oscillators must employ

a)

Possitive feedback

.

b)

Negative feedback

.

c)

Neither negative nor positive feedbacks

.

70.

Oscillations occur with

a)

Positive feedback having unity loop gain

b)

Positive feedback having unity loop

c)

Negative feedback having unity loop gain

71.

Oscillator generally used to generate RF is

a)

Hartley oscillator

b)

RC phase shift oscillator

72.

The type of oscillators used in the simple radio receivers are

a)

Phase shift type

b)

Colpitt's type

73.

An oscillator is a ... device

a)

Rotating

b)

Non-rotating

74.

An oscillator circuit is mainly ..... converter

a)

A.C. to A.C.

b)

D.C. to D.C.

c)

A.C. to D.C.

d)

D.C. to A.C.

75.

Which oscillator uses a tapped coil in its tank circuit?

a)

Hartley oscillator

b)

RC phase shift oscillator

c)

Colpitts oscillator

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