Question

In a study of transistor as an amplifier, the ratio of collector current to emitter current is 0.98. The collector current is 3mA, then base current will be approximately ______.

Options

• 6µA

• 6mA

• 60µA

• 60mA

Answer 1

In a study of transistor as an amplifier, the ratio of collector current to emitter current is 0.98. The collector current is 3mA, then base current will be approximately 60µA.

Explanation: 

`"i"_"c"/"i"_"e" = 0.98   "i"_"c"` = 3mA i_b = ?

`"i"_"c"/("i"_"c" + "i"_"b") = 0.98 = 98/100 => ("i"_"c" + "i"_"b")/"i"_"c" = 100/98`

1 + `"i"_"b"/"i"_"c" = 100/98     therefore "i"_"b"/"i"_"c" = 2/98  therefore  "i"_"b" = 3 xx 2/98 = 3/49` mA

= `3000/49` µA = 61.22 µA `approx` 60 µA