Bipolar transistor question

  • Thread starter nhrock3
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  • #1
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why we over dope one side of the transistor
why it lookes like
N+ P N

why not just
N P N
?
 

Answers and Replies

  • #2
1,161
82
To get high injection efficiency resulting in high beta value ("hfe" on data sheet). An "n-p-n" device would have a low beta, near 1, resulting in amplifiers with poor current gain. But an "n+-p-n" device has a large beta value, on the order of 50 to 500, resulting in amplifiers with high values of current gain.

Did that help?

Claude
 

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