\documentclass{standalone}
\usepackage{amsmath}  % For math
\usepackage{amssymb}  % For more math

\usepackage{blox}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\bXInput{A}
\bXComp{B}{A}
\bXLink[$R(s)$]{A}{B}
\bXBloc[2]{C}{$\displaystyle G(s)$}{B}
\bXLink{B}{C}
\bXOutput[4]{E}{C}
\bXLink[$C(s)$]{C}{E}
\bXReturn{C-E}{B}{}
\end{tikzpicture}

\end{document}