Instrumentation Transducers

Feedback Transducer System

Question 1
Marks : +2 | -2
Pass Ratio : 100%
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?
50 Ω
60 Ω
40 Ω
100 Ω
Explanation:
For a negative feedback system input impedance increases after feed backing.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Input impedance can be _______________ on application of negative feedback.
Increased
Decreased
Halved
Maintained constant
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).
Question 3
Marks : +2 | -2
Pass Ratio : 100%
In which of the following conditions, feedback gain (Af) become independent of forward gain (A)?
Aβ<<1
Aβ=1
Aβ>>1
Aβ=0
Explanation:
Expression for feedback gain in a negative feedback loop is given by;
Question 4
Marks : +2 | -2
Pass Ratio : 100%
Which of the following change has been happened to output impedance in the negative feedback system?
Increases
Decreases
No change
Negative
Explanation:
Output impedance with feedback in a negative feedback system is given by:
Question 5
Marks : +2 | -2
Pass Ratio : 100%
Difference between input signal and feedback signal is known as ____________
Feedback factor
Error signal
Output signal
Input signal
Explanation:
Error signal is the difference between the input signal and feedback signal. For a negative feedback loop error signal is given by:
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Which of the following represents complete expression for a closed loop system?
Aβ
A/ Aβ
A/ (1+Aβ)
1/ (1+Aβ)
Explanation:
A/(1+Aβ) represents closed loop gain for negative feedback system, for positive feedback system closed loop gain will be A/(1+Aβ).
Question 7
Marks : +2 | -2
Pass Ratio : 100%
In a feedback gain equation, what does the term β stands for?
Feedback gain
Forward gain
Open loop gain
Closed loop gain
Explanation:
The term β stands for feedback gain and it is the gain of feedback system only.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Voltage gain improves on the application of negative feedback.
True
False
Explanation:
Voltage gain with feedback network is given by Af = A/(1+Aβ), In which gain decreased by a factor 1+Aβ.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Error signal in positive feedback system will be ____________ input signal.
Greater than
Lower than
Equal to
Negative of
Explanation:
In positive feedback, signal is added with input signal and obtained error signal.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
For a negative feedback system, A=3 and β=2 and output impedance without feedback are 100Ω. What will be its total output impedance?
14.3 Ω
700 Ω
33.33 Ω
50 Ω
Explanation:
Output impedance with feedback in a negative feedback system is