## OSCILLATORS Questions with Answers :-

1. An oscillator converts ……………..

1. c. power into d.c. power
2. c. power into a.c. power
3. mechanical power into a.c. power
4. none of the above

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

1. LC tank circuit
2. Biasing circuit
3. Transistor
4. None of the above

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

1. Minimum
2. Maximum
3. Half-way between maximum and minimum
4. None of the above

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

1. Proportional to square of
2. Directly proportional to
3. Independent of the values of
4. Inversely proportional to square root of

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

1. Damped
2. Undamped
3. Modulated
4. None of the above

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

1. Positive
2. Negative
3. Neither positive nor negative
4. Data insufficient

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

1. High
2. Audio
3. Very low
4. Very high

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

4. None of the above

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

1. Two
2. Three
3. Four
4. None of the above

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

1. L and C
2. R, L and C
3. R and C
4. None of the above

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

1. Only positive
2. Only negative
3. Both positive and negative
4. None of the above

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

1. A voltage developed because of mechanical stress
2. A change in resistance because of temperature
3. A change in frequency because of temperature
4. None of the above

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

1. Positive
2. Zero
3. Negative
4. None of the above

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

1. Rigidity
2. Vibrations
3. Low Q
4. High Q

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

3. AF sweep generator
4. None of the above

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

1. Has more gain
2. Requires no input signal
3. Requires no d.c. supply
4. Always has the same input

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

1. A phase shift around the feedback loop of 180o
2. A gain around the feedback loop of one-third
3. A phase shift around the feedback loop of 0o
4. A gain around the feedback loop of less than 1

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

1. A gain of 1 around the feedback loop
2. No gain around the feedback loop
3. The attention of the feedback circuit must be one-third
4. The feedback circuit must be capacitive

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

1. 1
2. 01
3. 10
4. 02

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

1. 1
2. Greater than 1
3. Less than 1
4. Equal to attenuation of feedback circuit

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

1. Remains the same
2. Decreases
3. Increases
4. Insufficient data

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

1. By magnetic induction
2. By a tickler coil
3. From the centre of split capacitors
4. None of the above

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

1. 100
2. 1000
3. 50
4. More than 10,000

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

1. It has superior electrical properties
2. It is easily available
3. It is quite inexpensive
4. None of the above

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

1. Phase-shift oscillator
2. Hartely-oscillator
3. Colpitt’s oscillator
4. Crystal oscillator

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

1. Increased 2 times
2. Decreased 4 times
3. Increased 4 times
4. Decreased 2 times

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

1. Its low output
2. Its high Q
3. Less availability of quartz crystal
4. Its high output