# Instrumentation Transducers Questions and Answers – Feedback Transducer System

This set of Instrumentation Transducers Multiple Choice Questions & Answers (MCQs) focuses on “Feedback Transducer System”.

1. Difference between input signal and feedback signal is known as ____________
a) Feedback factor
b) Error signal
c) Output signal
d) Input signal
View Answer

Answer: b
Explanation: Error signal is the difference between the input signal and feedback signal. For a negative feedback loop error signal is given by:
e(t)=xi(t) – xf(t).

2. Error signal in positive feedback system will be ____________ input signal.
a) Greater than
b) Lower than
c) Equal to
d) Negative of
View Answer

Answer: a
Explanation: In positive feedback, signal is added with input signal and obtained error signal.

3. Which of the following represents complete expression for a closed loop system?
a) Aβ
b) A/ Aβ
c) A/ (1+Aβ)
d) 1/ (1+Aβ)
View Answer

Answer: c
Explanation: A/(1+Aβ) represents closed loop gain for negative feedback system, for positive feedback system closed loop gain will be A/(1+Aβ).
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4. Which of the following change has been happened to output impedance in the negative feedback system?
a) Increases
b) Decreases
c) No change
d) Negative
View Answer

Answer: b
Explanation: Output impedance with feedback in a negative feedback system is given by:
Rof = Ro/(1+Aβ).

5. Voltage gain improves on the application of negative feedback.
a) True
b) False
View Answer

Answer: b
Explanation: Voltage gain with feedback network is given by Af = A/(1+Aβ), In which gain decreased by a factor 1+Aβ.
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6. Input impedance can be _______________ on application of negative feedback.
a) Increased
b) Decreased
c) Halved
d) Maintained constant
View Answer

Answer: a
Explanation: Expression for input impedance on negative feedback is given by Rif=Ro(1+Aβ), in which it is increased by a factor (1+Aβ).

7. For a negative feedback system, A=3 and β=2 and output impedance without feedback are 100Ω. What will be its total output impedance?
a) 14.3 Ω
b) 700 Ω
c) 33.33 Ω
d) 50 Ω
View Answer

Answer: a
Explanation: Output impedance with feedback in a negative feedback system is
Rf=Ro/(1+Aβ).
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8. Input impedance of a system is 50 Ω, for the system to be negative feedback, which of the following can be its input impedance without feedback?
a) 50 Ω
b) 60 Ω
c) 40 Ω
d) 100 Ω
View Answer

Answer: c
Explanation: For a negative feedback system input impedance increases after feed backing.

9. In a feedback gain equation, what does the term β stands for?
a) Feedback gain
b) Forward gain
c) Open loop gain
d) Closed loop gain
View Answer

Answer: a
Explanation: The term β stands for feedback gain and it is the gain of feedback system only.
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10. In which of the following conditions, feedback gain (Af) become independent of forward gain (A)?
a) Aβ<<1
b) Aβ=1
c) Aβ>>1
d) Aβ=0
View Answer

Answer: c
Explanation: Expression for feedback gain in a negative feedback loop is given by;
Af= A/ (1+Aβ)
In which, when Aβ>>1, Af becomes reciprocal of loop gain β.

Sanfoundry Global Education & Learning Series – Instrumentation Transducers.

To practice all areas of Instrumentation Transducers, here is complete set of 1000+ Multiple Choice Questions and Answers.

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