\documentclass{standalone}

\usepackage{tikz,pgfplots}
\usepackage{siunitx}
\usepackage[siunitx,european]{circuitikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\usepackage{amsbsy}
\usetikzlibrary{fadings}
\usetikzlibrary{patterns}
\usetikzlibrary{automata,positioning}
\usepackage{mwe,subcaption,tikz}
\tikzset{boximg/.style={remember picture,red,thick,draw,inner sep=0pt,outer sep=0pt}}
\pgfplotsset{compat=1.11}
\begin{document}
\definecolor{mygreen}{rgb}{0,0.78,0}
\begin{tikzpicture}

	\draw[<->, thick] (0,3) node[above]{$U_{gs}$} |- (5,0) node[right]{$Q_g$};
	\draw[blue, thick] (0,0) -- (1.5,1.5) -- (3.5,1.5);
	\draw[blue, thick, dashed] (3.5,1.5) -- (5,2.5)
	(0.25,2.85) -- (0.75,2.85) node[black, right]{$U_{ds,1}$};
	\draw[blue, thick, dashdotted] (3.25,1.5) -- (4.75,2.5)
	(0.25,2.35) -- (0.75,2.35) node[black, right]{$U_{ds,2}$};
	\draw[blue, thick, dotted] (3,1.5) -- (4.5,2.5)
	(0.25,1.85) -- (0.75,1.85) node[black, right]{$U_{ds,3}$};
	\draw (3,0.75) node{$U_{ds,1}>U_{ds,2}>U_{ds,3}$};
	\draw[blue, thick, dashed] (1.5,1.5) -- (0,1.5) node[left]{$U_{miller}$};

\end{tikzpicture}
\end{document}