**OSCILLATORS Questions and Answers pdf :-**

1. An oscillator converts ……………..

c. power into d.c. power

c. power into a.c. power

mechanical power into a.c. power

none of the above

Answer : 2

2. In an LC transistor oscillator, the active device is ……………

LC tank circuit

Biasing circuit

Transistor

None of the above

Answer : 3

3. In an LC circuit, when the capacitor is maximum, the inductor energy is ……….

Minimum

Maximum

Half-way between maximum and minimum

None of the above

Answer : 1

4. In an LC oscillator, the frequency of oscillator is ……………. L or C.

Proportional to square of

Directly proportional to

Independent of the values of

Inversely proportional to square root of

Answer : 4

5. An oscillator produces……………. oscillations

Damped

Undamped

Modulated

None of the above

Answer : 2

6. An oscillator employs ……………… feedback

Positive

Negative

Neither positive nor negative

Data insufficient

Answer : 1

7. An LC oscillator cannot be used to produce ……………….. frequencies

High

Audio

Very low

Very high

Answer : 3

8. Hartley oscillator is commonly used in ………………

Radio receivers

Radio transmitters

TV receivers

None of the above

Answer : 1

9. In a phase shift oscillator, we use …………. RC sections

Two

Three

Four

None of the above

Answer : 2

10. In a phase shift oscillator, the frequency determining elements are …………

L and C

R, L and C

R and C

None of the above

Answer : 3

11. A Wien bridge oscillator uses ……………. feedback

Only positive

Only negative

Both positive and negative

None of the above

Answer : 3

12. The piezoelectric effect in a crystal is ……………

A voltage developed because of mechanical stress

A change in resistance because of temperature

A change in frequency because of temperature

None of the above

Answer : 1

13. If the crystal frequency changes with temperature, we say that crystal has ………….. temperature coefficient

Positive

Zero

Negative

None of the above

Answer : 1

14. The crystal oscillator frequency is very stable due to ………………. of the crystal

Rigidity

Vibrations

Low Q

High Q

Answer : 4

15. The application where one would most likely find a crystal oscillator is ……………..

Radio receiver

Radio transmitter

AF sweep generator

None of the above

Answer : 2

16. An oscillator differs from an amplifier because it ………

Has more gain

Requires no input signal

Requires no d.c. supply

Always has the same input

Answer : 2

17. One condition for oscillation is ………….

A phase shift around the feedback loop of 180o

A gain around the feedback loop of one-third

A phase shift around the feedback loop of 0o

A gain around the feedback loop of less than 1

Answer : 3

18. A second condition for oscillations is ……………….

A gain of 1 around the feedback loop

No gain around the feedback loop

The attention of the feedback circuit must be one-third

The feedback circuit must be capacitive

Answer : 1

19. In a certain oscillator Av = 50. The attention of the feedback circuit must be …………

1

01

10

02

Answer : 4

20. For an oscillator to properly start, the gain around the feedback loop must initially be

1

Greater than 1

Less than 1

Equal to attenuation of feedback circuit

Answer : 2

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

Remains the same

Decreases

Increases

Insufficient data

Answer : 3

22. In Colpitt’s oscillator, feedback is obtained …………….

By magnetic induction

By a tickler coil

From the centre of split capacitors

None of the above

Answer : 3

23. The Q of the crystal is of the order of …………

100

1000

50

More than 10,000

Answer : 4

24. Quartz crystal is most commonly used in crystal oscillators because ………….

It has superior electrical properties

It is easily available

It is quite inexpensive

None of the above

Answer : 1

27. ………….. is a fixed frequency oscillator

Phase-shift oscillator

Hartely-oscillator

Colpitt’s oscillator

Crystal oscillator

Answer : 4

28. In an LC oscillator, if the value of L is increased four times, the frequency of oscillations is …………

Increased 2 times

Decreased 4 times

Increased 4 times

Decreased 2 times

Answer : 4

29. An important limitation of a crystal oscillator is ……………

Its low output

Its high Q

Less availability of quartz crystal

Its high output

Answer : 1

30. The signal generator generally used in the laboratories is ………….. oscillator

Wien-bridge

Hartely

Crystal

Phase shift

Answer : 1