[sdiy] Transistor Question (simple I think)

[harrybissell]

Hello Scott:

I'm with Juergen... (5V rev.)

but there ARE things you can do...

You can place a reverse diode across the base-emitter
junction... it will conduct and protect the tranny.

You can put a diode in series with the emitter... then
it will block the reverse voltage.

You can limit the  current that can flow in the reverse
biased e-b junction, and let it break over if it wants...
We run e-b junctions in avalanche mode all the time
in noise sources... if the current is low enough it will
not degrade the tranny much.

If the tranny is a really highly specified device like
the MAT series (01, 02... one of those has no diodes
from e-b)... it could be degraded and the data sheet
says so.  2n3906... sure why not !!!

H^) harry

Scott Gravenhorst wrote:

> I have the data sheet for a 2N3906 PNP transistor and I'll
> be darned if I can find a spec for max reverse EB junction
> voltage.  The transistor will be used as a switch in an ADSR
> I'm trying to design, which if I'm successful, will comprise
> only one 4069 IC, 4 diodes and 3 or less transistors.  The
> way this transistor is used, it could have as much as 16
> volts of reverse bias for EB.  V(br)ebo says 5 volts, but I
> think that's forward.
>
> Help?
>
> =========================================================
> - What good are laws that only lawyers understand?
> - Government: The other religion.
> - The media's credibility should always be questioned.
> - Lambs who lie down with lions are lunch.
>
> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> -- Linux Rex         | RedWebMail by RedStarWare
> -- FatMan: home1.GTE.NET/res0658s/FatMan/
> -- NonFatMan: home1.GTE.NET/res0658s/electronics/