% Author: Dr. Matthias Jung, DL9MJ
% Year: 2020
\begin{circuitikz}[american]
    \draw (0,0) node[transformer core, yscale=0.95](T){};
    \draw (T.A1) to [short, -o] ++(0,0);
    \draw (T.A2) to [short, -o] ++(0,0);
    \draw (T.B1) to [stroke diode] ++(2.5,0) coordinate(e1);
    \draw (T.B2) to [short] ++(2.5,0) coordinate(e2);
    \draw (e1)   to [european resistor, v^=$U$, voltage=straight] (e2);

    \def\x{0.15}
    \draw[] (-1.3,-0.0) sin ++(\x, \x)
                        cos ++(\x,-\x)
                        sin ++(\x,-\x)
                        cos ++(\x, \x);
\end{circuitikz}