\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}
\usepackage{tikz}
\usetikzlibrary{arrows, calc, positioning,decorations.pathreplacing,shapes}

\begin{document}
\begin{preview}
\begin{tikzpicture}[scale=0.5]
	% verbindungen
	\draw (0,5) -- (2,5); % von a weg
	\draw (0,8) -- (6,8); % von b weg
	\draw (7,9) --(6,9) -- (6,3) -- (7,3);
	\draw (3,3) -- (2,3) -- (2,6) -- (7,6);

	\draw (3.25,3.75) -- (3.5,3.75) -- (3.5,4.25) -- (10,4.25);

	% Transistor left down
	\draw (3,2) -- (3,4);
	\draw[dashed] (3.25,2) -- (3.25,4);
	\draw (3.25,2.25) -- (3.5,2.25) -- (3.5,1) -- (7.5,1) -- (7.5,2.25) -- (7.25,2.25);
	\draw[latex-] (3.25,3) -- (4, 3); % Gate

	% Transistor right down
	\draw (7,2) -- (7,4);
	\draw[dashed] (7.25,2) -- (7.25,4);
	\draw[latex-] (7.25,3) -- (8, 3); % Gate

	\draw (7.25,3.75) -- (7.5,3.75) -- (7.5,5.25) -- (7.25,5.25);

	% Transistor right middle
	\draw (7,5) -- (7,7);
	\draw[dashed] (7.25,5) -- (7.25,7);
	\draw[-latex] (7.25,6) -- (8, 6); % Gate

	\draw (7.25,6.75) -- (7.5,6.75) -- (7.5,8.25) -- (7.25,8.25);

	% Transistor right top
	\draw (7,8) -- (7,10);
	\draw[dashed] (7.25,8) -- (7.25,10);
	\draw (7.25,9.75) -- (7.5,9.75) -- (7.5,11);
	\draw[-latex] (7.25,9) -- (8,9); % Gate

	% GND
	\node (GND-label) at (8,0){GND};
	\draw (6,0) -- (6,1);
	\draw (5,0) -- (7,0);
	\draw (5.2,-0.2) -- (6.8,-0.2);
	\draw (5.4,-0.4) -- (6.6,-0.4);

	\node (U-label) at (8.25,11){$U_{dd}$};
	\node (U-label) at (9.5,4.6){$a \overline{\lor} b$};
	\node (U-label) at (-0.5,8){$a$};
	\node (U-label) at (-0.5,5){$b$};

	\draw[fill=black] (6,8) circle (0.1);
	\draw[fill=black] (7.5,4.25) circle (0.1);
	\draw[fill=white] (0,5) circle (0.1);
	\draw[fill=white] (0,8) circle (0.1);
\end{tikzpicture}
\end{preview}
\end{document}