The current flowing into the base of a transistor is 100 μA. Find its collector current Ic, its emitter current Iɛ, and the ratio `\frac {I_C}{I_E}`. If the value of the current gain β is 100. Answer (10 mA, 10.1mA, 0.99) 




Given:

Base Current = `\I_B`  = 100 μA = 100 ｘ10⁻⁶ A

Current gain = β = 100



To Find:

1. Collector Current = `\I_C` = ?

2. Emitter Current = `\I_E` = ?

3. Ratio `\frac {I_C}{I_E}` = ?



Solution:


1. Collector Current = `\I_C` = ?


Using the Current gain β formula 


β = `\frac {I_C}{I_B}` 

or

`\I_C` = β ｘ `\I_B`

putting values

`\I_C` = 100 ｘ 100 ｘ10⁻⁶ A

`\I_C` = 1 ｘ10⁻² A

or

`\I_C` = 10 ｘ10⁻³  A

`\I_C` = 10 mA --------------Ans. (1)



2. Emitter Current = `\I_E` = ?

Since 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`
 
by putting values

`\I_E` =  100 ｘ10⁻⁶ A + 10 ｘ10⁻³  A

`\I_E` =  0.1 ｘ10⁻³ A + 10 ｘ10⁻³  A

`\I_E` =  10.1 ｘ10⁻³  A 

`\I_E` =  10.1 mA ------------Ans. (2)



3. Ratio `\frac {I_C}{I_E}` = ?

The required Ratio is 

`\frac {I_C}{I_E}` = `\frac {10 ｘ10⁻³ A}{10.1 ｘ10⁻³ A}`

`\frac {I_C}{I_E}` = 0.990 ---------------Ans. (3)



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