Discussion
Practical value of loop gain Aβ is always set slightly higher than 1 to compensate :
Answer: C
The key is Non-linearity, and texts give more than one reason for the margin.
An oscillator needs a loop gain \(A\beta = 1\) in steady state (the Barkhausen condition). In practice the loop gain is set a little above 1 so that oscillations start from noise and grow. As the amplitude rises, the non-linearity of the amplifier, for example saturation, lowers the average gain until it settles at 1. The key reads the question this way, with the margin taken up by the non-linearity.
Other books say the margin makes up for component ageing or losses. Noise is what starts the oscillation, not what the margin compensates, and a phase shift is removed by tuning the circuit to the frequency at which the loop phase is zero. Change in feedback voltage is not a standard answer. The choice follows the key.
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