question_answer

In a npn-transistor, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, then the emitter current will be :

A)  9 mA                                    

B)  11 mA

C)  1 mA                                    

D)  0.1 mA

Correct Answer: B

Solution :

                In an npn-transistor emitter current\[({{i}_{g}})\]is the sum of base current\[({{i}_{B}})\]and collector current\[({{i}_{C}})\].                 \[{{i}_{e}}={{i}_{B}}+{{i}_{c}}\] Given    \[\frac{90}{100}{{i}_{e}}={{i}_{c}}\]                                          ?.. (i) Also,      \[{{i}_{c}}=10\,mA\]                                  ...(ii) From Eqs. (i) and (ii), we get                 \[{{i}_{e}}=\frac{10\times 100}{90}=11\,mA\]