The current gain for a transistor working as a common-base amplifier is 0.96. If the emitter current is 7.2 mA, the base current will be

Current gain of transistor iswhere ∆iC is change in collector current, and ∆iE is change in emitter current. Given α=0.96. ∆iE=7.2,  ∆iC=0.96×7.2=6.91 mA Also ∆iE=∆iC+∆iB ∴∆iB =∆iE+∆iC=7.2-6.91=0.29 mA