\useasboundingbox (-1.5,-0.5) rectangle (6.25,6);
\draw[semithick] (0,0) rectangle (1.5,5);
\draw[semithick] (1.5,0) rectangle (5.0,5);
\draw[semithick] (1.5,0) -- (5.0,3.5);

\draw[thin,gray] (3,1.5) -- (3.5,1.5) -- (3.5,2);
\node[anchor=north,inner sep=1pt, font=\scriptsize] at (3.25,1.5) {1};
\node[anchor=west ,inner sep=1pt, font=\scriptsize] at (3.5,1.75) {1};

\node[rotate=90] at (0.75,2.5) {off};
\node[] at (4.0,0.75) {ohmic};
\node[] at (3.25,3.5) {saturation};

\node[anchor=north] at (0,0) {0};
\draw[thin] (0,0) -- (0,-0.075);
\node[anchor=east] at (0,0) {0};
\draw[thin] (0,0) -- (-0.075,0);

\node[anchor=north] at (1.5,0) {$V_{\mathrm{T}}$};
\draw[thin] (1.5,0) -- (1.5,-0.075);

\node[anchor=north] at (5.0,0) {$V_{\mathrm{GS,max}}$};
\draw[thin] (5.0,0) -- (5.0,-0.075);

\node[anchor=east] at (0,5) {$V_{\mathrm{DS,max}}$};
\draw[thin] (0,5) -- (-0.075,5);

\draw[{Latex[round,scale=1.2]}-{Latex[round,scale=1.2]},thick] 
  (0,5.75) -- (0,0) -- (6,0);

\node[anchor=south] at (6,0) {$V_{\mathrm{GS}}$};
\node[anchor=east] at (0,5.75) {$V_{\mathrm{DS}}$};