Question

In a silicon transistor, a change of `7.89 mA` in the emitter current produce a change of 7.8 mA in the collector current. What change in the base current is necessary to produce an equivalent change in the collector current?

Answer 1

Here, `DeltaI_(e)=7.89mA`,
`DeltaI_c=7.8mA, DeltaI_b=?`
As `alpha_(a.c.)=(DeltaI_c)/(DeltaI_(e))=7.8/7.89=0.9886`
Now `beta_(a.c.)=alpha_(a.c.)/(1-alpha_(a.c.))=0.9886/(1-0.9886)=86.72`
As `beta_(a.c.)=DeltaI_c//DeltaI_b`
` :. DeltaI_b=(DeltaI_c)/beta_(a.c.)=7.8/86.72`
`=89.94xx10^(-3)mA`