# Comparators and Waveform Generator MCQ

1. What is the Barkhausen criterion for oscillation?

A. Aß > 1

B. Aß < 1

C. Aß = 1

D. Aß ≠ 1

2. At what condition the output signal can be continuously obtained from the input signal?

A. When the product of input voltage and the feedback voltage is equal to 1

B. When the product of amplifier gain and transfer ratio is equal to 1

C. When the product of feedback voltage and transfer ratio is equal to 1

D. When the product of amplifier gain and the input voltage is equal to 1

3. An oscillator is a type of

A. Feedforward amplifier

B. Feedback amplifier

C. Waveform amplifier

D. RC amplifier

5. What is the condition to achieve oscillations?

A. |Aß| = 1

B. ∠Aß = 0^{o}

C. ∠Aß = multiples of 2π

D. All the mentioned

6. What happens if |Aß|<1?

A. Oscillation will die down

B. Oscillation will keep on increasing

C. Oscillation remains constant

D. Oscillation fluctuates

7. How sustained oscillation can be achieved?

A. Maintaining |Aß| slightly greater than unity

B. Maintaining |Aß| equal to unity

C. Due to the non-linearity of transistor

D. Due to using the feedback network

8. Why it is difficult to maintain Barkhausen’s condition for oscillation?

A. Due to variation in temperature

B. Due to variation in supply voltage

C. Due to variation in a components lifetime

D. All of the mentioned

9. Name the type of noise signal present in the oscillation?

A. Schmitt noise

B. Schottky noise

C. Saturation noise

D. None of the mentioned

10. A basic feedback oscillator is satisfying the Barkhausen criterion. If the ß value is given as 0.7072, find the gain of the basic amplifier?

A. 2.1216

B. 0.7072

C. 1

D. 1.414

11. The feedback signal of the basic sine wave oscillator is given as

A. V_{f} = Aß ×V_{o}

B. V_{f} = Aß ×V_{i}

C. V_{f} = Aß × (V_{o}/ V_{i})

D. V_{f} = Aß × (V_{i}/ V_{o})

12. Express the requirement for oscillation in polar form

A. Aß = 1∠360^{o}

B. Aß = 1∠90^{o}

C. Aß = 1∠π^{o}

D. Aß = 1∠270^{o}

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

A. 360^{o} phase shift

B. 180^{o} phase shift

C. 90^{o} phase shift

D. 60^{o} phase shift

14. How many RC stages are used in the RC phase shift oscillator?

A. Six

B. Two

C. Four

D. Three

15. Calculate the frequency of oscillation for the RC phase shift oscillator having the value of R and C as 35Ω and 3.7µF respectively.

A. 1230 Hz

B. 204 Hz

C. 502Hz

D. 673 Hz

16. What must be done to ensure that oscillation will not die out in the RC phase shift oscillator?

A. Gain of the amplifier is kept greater than 29

B. Gain of the amplifier is kept greater than 1

C. Gain of the amplifier is kept less than 29

D. Gain of the amplifier is kept less than 1

17. Calculate the feedback voltage from phase shift network.

A. V_{f} = ( V_{o}R^{3}S^{3}C^{3}) / (1+ 6SRC+5S^{2}C^{2}R^{2}+S^{3}R^{3}C^{3})

B. V_{f} = ( V_{o}R^{3}S^{3}C^{3}) / (1+ 5SRC+6S^{2}C^{2}R^{2}+S^{3}R^{3}C^{3})

C. V_{f} = ( V_{o}R^{3}S^{3}C^{3}) / (1+ 5SRC+5S^{2}C^{2}R^{2}+S^{3}R^{3}C^{3})

D. V_{f} = ( V_{o}R^{2}S^{3}C^{3}) / (1+ 6SRC+5S^{2}C^{2}R^{2}+S^{3}R^{3}C^{3})

18. Which type of op-amp is avoided for high frequencies?

A. LM318

B. Op-amp 741

C. LF 351

D. None of the mentioned

19. Find out the constant values of α and ß in phase shift oscillator.

A. α = √6, ß = -1/29

B. α = 6, ß = -1/29

C. α = √6, ß = 1/29

D. α = 6, ß = -1/29

20. A phase shift oscillator is designed to oscillate at 155Hz. Determine the value of R_{f}. (Take C = 0.30µF)

A. 399Ω

B. 3.98MΩ

C. 13.9 kΩ

D. 403 kΩ