In a common base circuit, the current gain is 0.96. If the collector current is 60 μA. Find the emitter current. Answer (62.5 μA)



Given:

Current gain = β =  0.96

Collector Current = `\I_C` =  60 μA = 60 ｘ10⁻⁶ A

To Find:

Emitter Current = `\I_E` =  ?



Solution:


The Emitter Current `\I_E` is the sum of the Base current `\I_B`  and collector current `\I_C` ie.

`\I_E` =  `\I_B`  + `\I_C`  -----------(1)


Where the base Current `\I_B` is unknown and can be found from the Current gain β formula which is 

β = `\frac {I_C}{I_B}` 

or

`\I_B` = `\frac {I_C}{β}` 

putting values

`\I_B` = `\frac {60 ｘ10⁻⁶ A}{0.96}`

`\I_B` = 62.5 ｘ10⁻⁶ A



Now putting the corresponding values in equation (1)

`\I_E` =  62.5 ｘ10⁻⁶ A  + 60 ｘ10⁻⁶ A

`\I_E` =  122.5 ｘ10⁻⁶ A  

or

`\I_E` =  122.5 μA  --------------Ans.

The  answer given in the book is the value of the Base Current `\I_B`, So the correct answer for `\I_E`  is  122.5 μA 



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