simple-example-tikz-circuit-library.tex

\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{0mm}

\usepackage{tikz}
\usetikzlibrary{circuits.logic.IEC}

\begin{document}
\begin{preview}
    \begin{tikzpicture}[circuit logic IEC]
        \node[and gate, inputs={normal,normal}] (myand) {};
        \draw (1,0) node[not gate, inputs={normal,normal}] (mynot) {};

        \draw (myand.input 1 -| -0.8,0) node[anchor=east]{P} -- (myand.input 1);
        \draw (myand.input 2 -| -0.8,0) node[anchor=east]{Q} -- (myand.input 2);

        \draw (myand.output) -- (mynot.input);
        \draw (mynot.output -| 1.8,0) node[anchor=west]{S} -- (mynot.output);
    \end{tikzpicture}
\end{preview}
\end{document}