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
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
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
Explanation: A/(1+Aβ) represents closed loop gain for negative feedback system, for positive feedback system closed loop gain will be A/(1+Aβ).
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
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
Explanation: Voltage gain with feedback network is given by Af = A/(1+Aβ), In which gain decreased by a factor 1+Aβ.
6. Input impedance can be _______________ on application of negative feedback.
a) Increased
b) Decreased
c) Halved
d) Maintained constant
View Answer
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
Explanation: Output impedance with feedback in a negative feedback system is
Rf=Ro/(1+Aβ).
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
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
Explanation: The term β stands for feedback gain and it is the gain of feedback system only.
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
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.
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