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\begin{eqnarray}
V_{GS}=\frac{R_{2}}{R_{1}+R_{2}}V_{IN}-V_{IN}
\end{eqnarray}
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\begin{eqnarray}
V_{GS}=V_{SUB}-V_{OUT}
\end{eqnarray}
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\frac{V_{IN}}{R_1+R_2}{\;}{<}{\;}h_{FE}I_B{\;}{\Leftrightarrow}{\;}\frac{V_{IN}}{R_1+R_2}\frac{1}{h_{FE}}{\;}{<}{\;}I_B
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