\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}

\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{shapes, calc, shapes, arrows} 

\tikzstyle{input}=[draw,fill=red!50,circle,minimum size=20pt,inner sep=0pt]
\tikzstyle{hidden}=[draw,fill=green!50,circle,minimum size=20pt,inner sep=0pt]
\tikzstyle{output}=[draw,fill=blue!50,circle,minimum size=20pt,inner sep=0pt]
\tikzstyle{bias}=[draw,dashed,fill=gray!50,circle,minimum size=20pt,inner sep=0pt]

\tikzstyle{stateTransition}=[->, thick]
\DeclareMathOperator{\xor}{XOR}
\begin{document}
\begin{preview}
\begin{tikzpicture}[scale=2]
	\node (x)[input] at (0,1) {$x$};
	\node (y)[input] at (0,0) {$y$};
	\node (h1)[hidden] at (1, 1.5) {$1$};
	\node (h2)[hidden] at (1, 0.5) {$2$};
	\node (h3)[hidden] at (1,-0.5) {$1$};
	\node (o1)[output] at (2,0.5) {$1$};

	\draw[stateTransition] (x) -- (h1) node [midway,above=-0.06cm] {$1$};
	\draw[stateTransition] (x) -- (h2) node [midway,above=-0.06cm] {$1$};
	\draw[stateTransition] (y) -- (h2) node [midway,above=-0.06cm] {$1$};
	\draw[stateTransition] (y) -- (h3) node [midway,above=-0.06cm] {$1$};

	\draw[stateTransition] (h1) -- (o1) node [midway,above=-0.06cm] {$1$};
	\draw[stateTransition] (h2) -- (o1) node [midway,above=-0.1cm] {$-2$};
	\draw[stateTransition] (h3) -- (o1) node [midway,above=-0.06cm] {$1$};

	\draw[stateTransition] (o1) -- (3.5,0.5) node [midway,above=-0.1cm] {$\xor(x, y)$};

\end{tikzpicture}
\end{preview}
\end{document}