Subject: Re: Transistors circuits by the thousands
References: <firstname.lastname@example.org> <email@example.com>
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Date: Mon, 06 Jan 2003 00:11:56 GMT
NNTP-Posting-Date: Sun, 05 Jan 2003 17:11:56 MST
On Sun, 05 Jan 2003 00:54:54 GMT, "Lukas Louw" wrote:
>If you must use these, why not use two of them connected as a Darlington,
>and you should be more than OK as far as gain is concerned. Sometimes this
>will make sense for small/medium production runs to reduce number of
>different part types you need to buy, and get a better price break on those
When I use the lowest datasheet value for the gain, the only way to
make it work was to pair them up. That was why I was wondering if I
can safely ignore the worst case specs.
>However, if your'e having these products made in the far east, they have
>access to many more devices than what we can get easily in the US. Assuming
>that you're using a good size OEM, they typically have so much buying power
>with the part manufacturers that it becomes a moot point to just spec a
>better device.Also remember that the 2N3904 CBE pinout, if used for the PCB
>layout will make it difficult for the factory to substitute a better part,
>as most of the small trannies over there use BCE pinouts............
>If I were you, I'd contact the factory and ask them who their preferred semi
>manufacturers are, and get them to send you some databooks or online
>datasheet URLs, and pick the right part for the job.
Those are very good suggestions. Thank you. I will certainly try to
that on the next project. The current one is just a modification to
an existing design. We are just beginning to work Far East
contractors. It is quite a culture shock :-)
>Just Google for Mospec, Sanken and KEC for starters, and have a look at what
>you can expect your factory to have access to. Don't bother with the North
>American distributor for Sanken, Allegro. They have their heads up their
>*sses. The other two don't have distribution here anyway.
>> In my design, the 3904 was "preferred", not because of the optimal
>> characteristics, but because of the fact that it was already used in
>> other area's in the existing circuit.