\begin{axis}[ xlabel=$\frac{V_{\mathrm{GS}}-V_{\mathrm{TH}}}{n V_{\mathrm{T}}}$
            , ylabel=$\mathrm{IC}$
            , ymode=log
            , xmin=-10
            , xmax=10
            , ymin=0.001
            , ymax=100
            , clip=true
            , grid=both
            , width= 12cm
            ]
  \draw[dashed] (axis cs:-10,0.1) -- (axis cs:10,0.1);
  \draw[dashed] (axis cs:-10,10) -- (axis cs:10,10);

  \addplot[ mark=none
          , domain=0.5:10
          , samples=100
          , smooth
          , gray
          , thick] {(x/2)^2}; 

  \addplot[ mark=none
          , domain=-10:-0.5
          , samples=100
          , smooth
          , gray
          , thick] {e^x};  

  \addplot[ mark=none
          , thick
          , domain=-10:10
          , samples=300
          , smooth
          , thick] {(ln(e^(0.5*x)+1))^2}; 

  \node[rotate=90,fill=white,font=\scriptsize, inner sep=2pt] 
    at (axis cs:-9,1) {moderate (M.I.)};
  \node[rotate=90,fill=white,font=\scriptsize, inner sep=2pt] 
    at (axis cs:-9,1e-2) {weak (W.I.)};
  \node[rotate=90,fill=white,font=\scriptsize, inner sep=2pt] 
    at (axis cs:-9,3e1) {strong (S.I.)};

  \draw[{Latex[round,scale=0.9]}-]
    (axis cs:1.05,1) -- (axis cs:0,3) 
    node[anchor=south,fill=white] {$\mathrm{IC}$};

  \draw[{Latex[round,scale=0.9]}-]
    (axis cs:0.9,2e-1) -- (axis cs:4,5e-1) 
    node[anchor=west,fill=white] {$\mathrm{IC}_{\mathrm{quad}}$};

  \draw[{Latex[round,scale=0.9]}-]
    (axis cs:-1.5,2.2e-1) -- (axis cs:-3.5,5e-1) 
    node[anchor=east,fill=white] {$\mathrm{IC}_{\mathrm{exp}}$};
\end{axis}