Physics - Semiconductors Question with Solution | TestHub

Here,

$\mathrm{\beta }=69$

${\mathrm{I}}_{\mathrm{E}}=7 \mathrm{mA}$

Since,$\mathrm{\beta }=\frac{\mathrm{\alpha }}{1-\mathrm{\alpha }}$

$69=\frac{\mathrm{\alpha }}{1-\mathrm{\alpha }}$

$69-69\mathrm{\alpha }=\mathrm{\alpha }$

$69=70\mathrm{\alpha }$

$\mathrm{\alpha }=\frac{69}{70}=0.986$

$\frac{{\mathrm{I}}_{\mathrm{C}}}{{\mathrm{I}}_{\mathrm{E}}}=0.986$

$\therefore {\mathrm{I}}_{\mathrm{C}}=0.986 {\mathrm{I}}_{\mathrm{E}}=0.986\times 7=6.9\mathrm{ }\mathrm{mA}$

$\therefore {\mathrm{I}}_{\mathrm{B}}={\mathrm{I}}_{\mathrm{E}}-{\mathrm{I}}_{\mathrm{C}}=7-6.9=0.1\mathrm{ }\mathrm{mA}$