The neutral base width of a bipolar transistor, biased in the active region, is $0.5 \; \mu \mathrm{m}$. The maximum electron concentration and the diffusion constant in the base are $10^{14} / \mathrm{cm}^{3}$ and $\mathrm{D}_{n}$ $=25 \mathrm{~cm}^{2} / \mathrm{sec}$ respectively. Assuming negligible recombination in the base, the collector current density is (the electron charge is $1.6 \times 10^{-19}$ coulomb)
- $800 \mathrm{~A/cm}^{2}$
- $8 \mathrm{~A/cm}^{2}$
- $200 \mathrm{~A/cm}^{2}$
- $2 \mathrm{~A/cm}^{2}$