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Out of the following. what happens to the overall gain of the system of a closed loop control system with positive value of feedback gain?
1. No effect
2. Increase
3. Decrease
4. Increase or Decrease

1 Answer

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Correct Answer - Option 2 : Increase

Concept of Feedback System:

  • A Feedback System is one in which the output signal is sampled and then fed back to the input to form an error signal that drives the system, and depending on the type of feedback used, the feedback signal which is mixed with the systems input signal, can be either a voltage or a current.
  • Feedback will always change the performance of a system and feedback arrangements can be either positive (regenerative) or negative (degenerative) type feedback systems.
  • If the feedback loop around the system produces a loop-gain that is negative, the feedback is said to be negative or degenerative with the main effect of the negative feedback is in reducing the system’s gain.
  • If however, the gain around the loop is positive, the system is said to have positive feedback or regenerative feedback. The effect of positive feedback is to increase the gain which can cause a system to become unstable and oscillate especially if GH = -1.

 

Positive feedback:

  • In an open-loop system, we do not have any feedback path but in a closed-loop system, we have a feedback path.
  • The transfer function of the closed-loop transfer function, with positive feedback, is given by \(\frac{{G\left( s \right)H\left( s \right)}}{{1 - G\left( s \right)H\left( s \right)}}\)
  • The overall gain of the transfer function increases with positive feedback. 

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