In an n-p-n transistor, the collector current is $$28 \mathrm{~mA}$$. If $$80 \%$$ of electrons reach the collector, its base current in $$\mathrm{mA}$$ is

When the conductivity of a semiconductor is only due to the breaking of the covalent bonds, the semiconductor is called

For a common emitter configuration, if '$$\alpha$$' and '$$\beta$$' have their usual meanings, the incorrect relation between '$$\alpha$$' and '$$\beta$$' is

For emission of light, a light emitting diode (LED) is