Question

In a common-base connection, the emitter current is 6.28mA and collector current is 6.20 mA. Determine the common base DC current gain.

Answer 1

Data : I_E = 6.28 mA, I_C = 6.20 mA

α_dc = \(\cfrac{I_C}{I_E}\) and β_dc = \(\cfrac{I_C}{I_B}\) = \(\cfrac{\alpha_{dc}}{1-\alpha_{dc}}\)

Common-emitter current gain, α_dc = \(\cfrac{6.20}{6.28}\) = 0.9873

Therefore, common-base current gain,

β_dc = \(\cfrac{0.9873}{1-0.9873}\) = \(\cfrac{0.9873}{0.0127}\) = 77.74

OR 

I_E = I_B + I_C 

∴ I_B = I_E – I_C = 6.28 – 6.20 = 0.08 mA

∴ β_dc = \(\cfrac{6.20}{0.08}\) = 77.5