I'd say it can be done with one transistor and
a very small coil with two windings...
:o)
-Roman


Russell McMahon wrote:
>
> > Requirement
> >
> > Step down voltage regulator suitable for powering small low voltage
> circuits
> > from a higher voltage supply with a reasonable power dissipation.
> >
> > Overall figure of merit = finished cost while meeting design
> specification.
> > Costing rules provided below.
> .................
>
> OK - here's a solution that has been suggested by a friend from the NatSemi
> LM336 regulator diode data sheet
>
> Without going back to my original cost list I estimate that this is about
> 130 to 150 units cost. (Under $US1 probably with substitutions below). Not
> too bad.
> I've pretended that the LM336 here can be substituted with a low cost zener
> diode - if not the price is significantly higher.
> I've assumed that all transistors can be low cost general purpose ones BC337
> / BC327 as the power level specified in my challenge is low.
> Also, the output catch diode could be a 1N4148 ! - not what you would
> normally see in this role but again, the power level is low.
>
> Any improvements on this?
>
>         Russell McMahon
>
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>
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