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transistor substitute? Answered

can i use bd 139 instead of bc 547

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user
iceng (author)2012-09-05

BD139 is 80V, 1.5A, NPN TO-126,  Minimum gain @ 5ma = 25......
BC547 is 45V, 100ma, NPN TO-92, Minimum gain@  2ma  = 110

So a low order Yes as a general purpose application
But not for a high FQ application and not a direct replacement.

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user
quatch (author)iceng2012-09-05

How do you tell the 'high FQ' (frequency?) part?

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user
iceng (author)quatch2012-09-05

Well, the BC547 specifies a gain bandwidth fT product at 300 MHz
and has numbers for input Cib & output Cob capacitance which leads
me to think the transistor might be used in a radio or some other high
frequency circuitry.

The PDF for the BD139 never mentions  the above parameters.

You can read the PDFs for your self by clicking on the red pointers
in this comment.

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steveastrouk (author)2012-09-05