At 04:15 AM 6/12/2008, you wrote:
>PicDude wrote:
>
> > Hadn't factored in the internal protection diodes, thanks.
> > I need to do this with 8 outputs, and only one OC output.  I started with a
> > 2 transistor circuit (1 NPN + 1 PNP), but thought I could simplify it this
> > way.
>
>Yeah, or add a ULN2003/2803 ?

Sure.

For a single channel, there are integrated transistor/resistor combos that
will do the NPN thing. Some duals might even do the whole thing, maybe
with an external resistor to control Ib, but the choices are getting a bit
thinner for reliable operation at 250mA. If you don't mind non-jellybean
parts, there's even an integrated SMT N-channel MOSFET (with pull-down)
and PNP BJT that comes close (with an external resistor for Ib).

No good integrated bipolar high-side drivers AFIR, since it's difficult
to make a good PNP transistor in an IC.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



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