Block diagram in electrical circuit

\documentclass[margin=3mm]{standalone}
\usepackage{circuitikz}
\usepackage{amsmath}          % <---
\newcommand\ds{\displaystyle} % <---

\begin{document}
    \begin{circuitikz}[scale=3, european]
\draw (0,1) to [R=$R$] ++ (1,0)
            to [L=$L$] ++ (1,0)
            to [C=$C$] ++ (1,0)
            to [short,i=$i(t)$] ++ (0,-1)
            to [twoport,t=\Large $G$, 
                l={$\xrightarrow[\ds u_e(t)]{}$}]   (0,0) % <---
            -- (0,1);
\end{circuitikz}
\end{document}

gives:

addendum:

If you like to have circuit's elements on opposite side, than you can write:

\draw (0,1) to [R,a=$R$] ++ (1,0)
            to [L,a=$L$] ++ (1,0)
            to [C,a=$C$] ++ (1,0)
            to [short,i=$i(t)$] ++ (0,-1)
            to [twoport,t=\Large $G$,
                l={$\xrightarrow[\ds u_e(t)]{}$}]   (0,0) % <---
            -- (0,1);

or

\draw (0,1) to [R,l_=$R$] ++ (1,0)
            to [L,l_=$L$] ++ (1,0)
            to [C,l_=$C$] ++ (1,0)
            to [short,i=$i(t)$] ++ (0,-1)
            to [twoport,t=\Large $G$,
                l={$\xrightarrow[\ds u_e(t)]{}$}]   (0,0) % <---
            -- (0,1);

in both cases the result is the same: