Question

Consider the feedback system shown in the figure. The Nyquist plot of $G\left(s\right)$ is also shown. Which one of the following conclusion is correct?

• A. $G\left(s\right)$ is an all-pass filter
• B. $G\left(s\right)$ is a strictly proper transfer function
• C. $G\left(s\right)$ is a stable and minimum-phase transfer function
• D. The closed -loop system is unstable for sufficiently large and positive $K$

Answer 1

The correct option is D The closed -loop system is unstable for sufficiently large and positive $K$


From the Nyquist plot, it can be seen that it does not encircle the critical point $(-1,0).$
$N=P-Z,N=0$
The closed loop system is unstable for sufficiently large and positive $K$.