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after a quick check with some datasheets, it seems
1) BF494 and BF199 are not drop-in (i.e. 100% compatible, at least in elec specs). Hfe and cut-off frequencies are different. The latter is bigger in BF199. These can be problematic in some RF application.
2) Similary 549 and 547 have also some differencies, like Vceo, Vcbo, NF etc. Theoretically in some applications (as long as you have enough design-margin, e.g. in NF and max volatges), you can use them as two solutions, But you should be careful.
It is difficult to make any detailed analysis, as your application requirements can be tricky. But surely they are not 100% drop-in to each other.
You're probably ok-ish with both of these replacements, although of course it depends on the
circuit (some circuits may be more critical than others). You'll probably be fine. I take it this is for some AM or FM receiver, right?
EDIT: Agree with Hakeen, our posts overlapped. Chances are you'll be fine, but if a circuit was exploiting the BF199
characteristics specifically, then the BF494 might not work.
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