# EE AND ECE IMPORTANT MCQ PDF-Oscillators 1

Q1. An oscillator converts ……………..

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

Q2. In an LC transistor oscillator, the active device is ……………

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

Q3. 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

Q4. 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

Q5. An oscillator produces……………. oscillations

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

Q6. An oscillator employs ……………… feedback

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

Q7. An LC oscillator cannot be used to produce ……………….. frequencies

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

Q8. Hartley oscillator is commonly used in ………………

4. None of the above

Q9. In a phase shift oscillator, we use …………. RC sections

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

Q10. 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

Q11. A Wien bridge oscillator uses ……………. feedback

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

Q12. 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

Q13. 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

Q14. The crystal oscillator frequency is very stable due to ………………. of the crystal

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

Q15. The application where one would most likely find a crystal oscillator is ……………..

3. AF sweep generator
4. None of the above

Q16. 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

Q17. 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

Q18. 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

Q19. In a certain oscillator Av = 50. The attention of the feedback circuit must be …………

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

Q20. 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

Q21. 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

Q22. 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

Q23. The Q of the crystal is of the order of …………

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

Q24. 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

Q25. ………….. is a fixed frequency oscillator

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

Q26. 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

Q27. 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