 It is defined as the ratio of the output current ( collector current ) and input current ( emitter current ).
 It is ratio of the change in collector current to the change in emitter current at constant collector – base voltage ( V_{CB} ).
α = ∆I_{C} / ∆I_{E}………..
( 1 )
 It is defined as the ratio of the output current ( emitter current ) and input current ( base current ).
 It is ratio of the change in emitter current to the change in base current.
γ = ∆I_{E} / ∆I_{B}………….(
2 )
Relation between
α and γ
As I_{E}
= I_{C} + I_{B}
∆I_{E} =
∆I_{C} + ∆I_{B}
Therefore ∆I_{B}
= ∆I_{E} – ∆I_{C}………. ( 3 )
From equation (
2 ) and ( 3 )
γ = ∆I_{E}
/ ∆I_{E} – ∆I_{C}
Divide numerator
and denominator by ∆I_{E}
γ = [ ∆I_{E}
/ ∆I_{E} ] / [ ∆I_{E} –
∆I_{C} ] / ∆I_{E}
= 1 / ( 1 – α )

γ ( 1 – α ) = 1
γ – γα = 1
γ – 1 = γα
α = ( γ – 1 ) / γ

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