% Author: Dr. Matthias Jung, DL9MJ
% Year: 2021
\begin{circuitikz}
    \draw[-Triangle](0,0) -- (5.0,0.0) 
        node[anchor=north east] () {$\frac{f}{\mathrm{kHz}}$};
    \draw[-Triangle](0.0,0.0) -- (0.0,3.0)
        node[anchor=north east] () {$U_\mathrm{A}$};
    \draw(0.6,-0.40) node[] () {0{,}3};
    \draw(2.5,-0.40) node[] () {3{,}0};

    \draw[rounded corners=3mm, thick, black]
        (0.3,0) -- ++(0.3,2.5) 
                -- ++(1.9,0)
                -- ++(0.3,-2.5);

    \draw [dashed] (0.6,0) -- ++(0,3);
    \draw [dashed] (2.5,0) -- ++(0,3);    
\end{circuitikz}