The formula to the right of the = symbol in the first row comes reasonably close to the screenshot you posted, including the use of small outer square brackets and large inner curly braces. However, I do not recommend this look. The "look" of the second row may be more appealing to your readers.
I think flalign* and \intertext{} are very good for you.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{flalign*}
& & T_{Loop Filter}(s)&=K_{p}+\frac{K_{i}}{s} & & \\
\intertext{The overall transfer function of given PLL can be given as}
& & \frac{{\phi}_{c}(s)}{{\phi}(s)}&=\frac{T_{Loop Filter}(s)*\frac{1}{s}}{1+\frac{T_{Loop Filter}}(s)*\frac{1}{s}} & & \\
& & \frac{\phi_{c}(s)}{\phi(s)}&=\frac{K_{p}(s)+K_{i}}{s^{2}+K_{p}(s)+K_{i}} & &
\intertext{In general transfer function for a second order closed loop control system is given as}
& & T_{second order}&=\frac{{\omega}^2+{2{\delta}}{\omega}s}{s_{2}+2{\delta}{\omega}s+{\omega}^{2}} & & \\
& \rlap{\text{On comparing}} & {\omega}&={sqrt{K_i}} {\delta}=\frac{K_p}{2\sqrt{K_{i}}} & &
\end{flalign*}
\end{document}
Best Answer
The formula to the right of the
=
symbol in the first row comes reasonably close to the screenshot you posted, including the use of small outer square brackets and large inner curly braces. However, I do not recommend this look. The "look" of the second row may be more appealing to your readers.