# Closed-Loop Frequency Response and Circuit Stability MCQ’s

This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Closed-Loop Frequency Response and Circuit Stability”.

1. Calculate the value of open loop frequency response curve at any point beyond break frequency in 741C op-amp?
a) 1000000Hz
b) 1000Hz
c) 10000000Hz
d) 100000Hz

2.

Frequency response of µA709C for various closed loop gain is shown. Choose the curve that has wider bandwidth and high gain?
a) Curve 4
b) Curve 3
c) Curve 2
d) Curve 1

3. Open loop configuration is not preferred in op-amps because
a) First break frequency is too large
b) First break frequency is very small
c) Second break frequency is too large
d) All of the mentioned

4. When does a system said to be stable?
a) Output reaches a minimum value at finite time
b) Output reaches a maximum value at any time
c) Output reaches a fixed value at finite time
d) Output reaches a fixed value at any time

5. How is the criterion for the system determined?
a) Graphical method
b) Theoretical method
c) Analytical method
d) All of the mentioned

6. “Transfer function” in control system refers to
a) Feedback block
b) Content of each block
c) Forward block
d) Input and output blocks

7. Why unstable systems are considered to be impractical?
a) None of the mentioned
b) Output decreases with time
c) Output reaches fixed value
d) Output increases with time

8. A standard block diagram of closed loop system composes of
a) Two blocks
b) Single block
c) Three blocks
d) None of the mentioned

9. Which method is considered to be a graphical method in testing the system?
a) Bode plot
b) Routh-Hurwitz criteria
c) Circuit testing
d) None of the mentioned

10. Name the block connected in the feedback path
a) Feedback block
b) Forward block
c) Output block
d) Summation of feedback, forward and output block

11. Mention the phase condition that leads to sustained oscillation
a) ∠-Aß =0
b) All of the mentioned
c) ∠-Aß = multiple of 2π
d) ∠Aß = odd multiple of π

12. Measure taken to increase the bandwidth of an op-amp.
a) Increase the frequency for the configuration
b) Reduce the gain of the configuration
c) Closed loop configuration is used
d) Open loop configuration is used

13. When the magnitude of (AoL )×( ß ) = 0dB, state the condition at which system become stable?
a) Phase angle is > -180o
b) Phase angle is < -180o
c) Phase angle is > +180o
d) Phase angle is < +180o

14. Determine the state of the system

a) Stable system
b) Unstable system
c) Casual system
d) Bounded system

15. Find out the system stability when a system has three RC poles pairs
a) Attain stability at low frequency
b) Attain stability at high frequency
c) Attain instability at high frequency
d) Attain instability at low frequency

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