The Nyquist criterion for stability states that an amplifier is unstable if the Nyquist curve encloses the -1 + j0 point, and the amplifier is stable if the curve does not enclose this point. If Aβ

Nyquist criterion: The Nyquist stability criterion is often expressed in terms of the open-loop transfer function �(�)�(�). The criterion states that if 1+�(�)�(�) has no poles in the right-half plane (RHP), the system is stable. Mathematically, this is equivalent to saying that the Nyquist plot should not encircle the -1 + j0 point.

• This is consistent with the Nyquist stability criterion, which states that if the Nyquist curve does not enclose the point -1 + j0 (i.e., the -1 point on the real axis), then the system is stable.
• If the curve encloses this point, the system is unstable. The condition\(|1\times A\beta| <1\) is used to determine the stability of the system based on the Nyquist plot.

Here, option 3 is correct.