In a `PNP` transistor working as common-base amplifier, current gain is `0.96` and current is `7.2 mA`. The base current is

Options

A. `0.42 mA`
B. `0.49 mA`
C. `0.29 mA`
D. `0.35 mA`

Answer

C

Explanation

Current gain in common-base amplifer is ratio of charge in collector to charge in emitter current.
Current gain of transistor is
`alpha = (deltai_(C))/(Deltai_(E))`
where, `Deltai_(C)` is change in collector current, and `Deltai_(E)` is change in emitter current.
Given, `alpha = 0.96, Deltai_(E) = 7.2`,
`Deltai_(C) = 0.96 xx 7.2 = 6.91 mA`
Also `Deltai_(E) = Deltai_(C) + Deltai_(B)`
`:. Deltai_(B) = Deltai_(E) - Deltai_(C) = 7.2 -6.91 = 0.29mA`