Question

The neutral base width of a bipolar transistor , biased in the active region, is $0.5\mu m$. The maximum electron concentration and the diffusion constant in the base are ${10}^{14}/c{m}^3$ and $D_n=25c{m}^2/sec$ respectively. Assuming negligible recombination in the base ,the collector current density is (the electron charge is $1.6\times {10}^{-19}$ Coulomb )

• A. $2A/c{m}^2$
• B. $800A/c{m}^2$
• C. $8A/c{m}^2$
• D. $200A/c{m}^2$

Answer 1

The correct option is C $8A/c{m}^2$

Ans : (b)

$J_c=q{D}_n\frac{dn}{dx}$
$=1.6\times {10}^{-19}\times 25\times \frac{{10}^{14}}{0.5\times {10}^{-4}}$
$J_c=8A/c{m}^2$