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प्रश्न
What are α and β parameters for a transistor? Obtain a relation between them.
उत्तर
Alpha (αdc): It is defined as the ratio of collector current to emitter current.
`alpha_(dc)="I"_c/"I"_E` -----------------(Equation 1)
Beta (βdc): It is the current gain defined as the ratio of collector current to the base current.
`beta_(dc)="I"_c/"I"_B` --------------------(Equation 2)
Relation between αdc and βdc:
For a transistor,
IE = IB + IC (with Ic ≅ IE) -----------(Equation 3)
Divinding both the side of eqn.(3) with Ic ,we get :
`"I"_E/"I"_c="I"_B/"I"_C+1`
`1/alpha_(dc)=1/beta_(dc)+1`
`alpha_(dc)=beta_(dc)/(1+beta_(dc))` -----------------------(Equation 4)
Or, `beta_(dc)=alpha_(dc)/(1-alpha_(dc))` ----------------------(Equation 5)
Equations (4) and (5) give the relation between αdc and βdc of a transistor.
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Figure 1
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