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I have some questions about BJT datasheet. Please help ...

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nnvkct

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In the datasheet, hfe parameter is a variant quantity. Of course, in real circuit hfe should an invariant quantity. How to fix it ? Please give me an example about a circuit in which hfe quantity is mostly invariant.
My second question is: "what's the meaning of Cob parameter?"

I appreciate any help. Thanks.
 

Re: I have some questions about BJT datasheet. Please help .

HFE is beta of the transistor
IC = beta IB in active region

cob i'm not sure
 

yes maybe you are right, current gain beta is a function of its collector current,
you can check this information on P.R.gray's book ,p115

and beta is also a function of temperature ,normaly beta has postive temperature co-efficience, so bjt have sef-calefaction. this is the reason that bjt power transistor is not used parallel to supply big current and need thermal protection circuit to protect the power transistor.

i am not sure if you have get your answer??
 

cob or cobo is the output capacitance

it is in the range of PF "pico farad"

it is the capacitance between base and collector


there is also input capacitance between base and emitter
 

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    nnvkct

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