Discussion
Identify the correct sequence of the following with increasing value of gain :
(i) Amplifier without feedback
(ii) Amplifier with positive feedback
(iii) Oscillator
(iv) Amplifier with negative feedback
Codes :
Answer: C
In increasing order of gain the sequence is (iv), (i), (ii), (iii).
Negative feedback reduces gain to \(A/(1 + A\beta)\), so the amplifier with negative feedback has the least gain. The amplifier without feedback has its open-loop gain A. Positive feedback increases gain to \(A/(1 - A\beta)\), larger than A while Aβ is less than 1. An oscillator is the limit where Aβ = 1, so the gain becomes infinite and the circuit produces an output with no input.
The other codes misplace at least one of these, for example by putting the oscillator before the amplifiers or starting from the amplifier without feedback.
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