search for switchers

Harry Bissell harrybissell at
Thu Nov 25 07:23:08 CET 1999

Another technique is to use two MOS switches in series, connected together
drain to drain (or source to source) and use the pesky reverse diode that
way. I saw this in a "Design Idea" or "Idea for Design". You can pass an AC
wave with this arrangement. It looks crazy but it works. I've tried it in
both spice simulation and real life...
OTOH, one good switch might be better... but I have a lot of cheap leftover
n channel MOS trannys so why not. I used the VN1206 for integrator reset on
a VCO.

:^) Harry

Jim Patchell wrote:

>     My preference for MOS transistors as switchs is to use the ones with
> the bulk connection.  These are by far the most useful as this
> eliminates that pesky parasitic diode from the drain to source (you tie
> the bulk to the lowest potential, usually V-).  As far as the two you
> have listed, I have no experience with those devices, but those would be
> the first two I would try.
>     -Jim
> Martin Czech wrote:
> > On the search for good switchers I found the following NMOST:
> >
> > BS170 (bulk to source)
> > BS107 (bulk to source)
> > BFR29 (bulk connection)
> > BSV81 (bulk connection, low Igs, low Isd)
> >
> > All seem to have no ESD-protection, this is good, because
> > virtually no Igs, Igd, Igb. Of course only if you don't
> > zap them.
> >
> > Any experiences, comments on those?
> >
> > m.c.

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