[sdiy] Transistor Question (simple I think)

[harrybissell]

I'd have said..

"the ubiquitous 1N4148... will do"   ;^)

H^) harry

Scott Gravenhorst wrote:

> harrybissell <harrybissell at prodigy.net> wrote:
> >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.
>
> This sounds like what I need.  Thanks.  I assume a lowly 1N4148
> would do?
>
> >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/
> >
>
> =========================================================
> - 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/