elektroda.net NewsGroups Forum Index - Electronics Design - Adjustable voltage source from 0 to 12V
Ecnerwal
Guest
Guest
Sun Feb 14, 2010 9:01 pm
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Quote:
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Last I recall, the LM317 application notes include this circuit - all
you need is to pull the reference negative. Page 16 of the PDF, typical
applications, 0-30V regulator. LM317 datasheet is really LM117 datasheet
(they are a family). National Semi website or your favorite source of
datasheets.
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Cats, coffee, chocolate...vices to live by
Jim Thompson
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Guest
Sun Feb 14, 2010 9:15 pm
On Sun, 14 Feb 2010 14:01:59 -0500, Ecnerwal
<MyNameForward_at_ReplaceWithMyVices.Com.invalid> wrote:
Quote:
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Last I recall, the LM317 application notes include this circuit - all
you need is to pull the reference negative. Page 16 of the PDF, typical
applications, 0-30V regulator. LM317 datasheet is really LM117 datasheet
(they are a family). National Semi website or your favorite source of
datasheets.
OBones <obones_gfd__at__gfd_altern.org> wrote:
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Last I recall, the LM317 application notes include this circuit - all
you need is to pull the reference negative. Page 16 of the PDF, typical
applications, 0-30V regulator. LM317 datasheet is really LM117 datasheet
(they are a family). National Semi website or your favorite source of
datasheets.
But you need a negative supply. Perhaps a good place for a charge
pump, since the current needs of the ADJ pin are less than 100uA.
...Jim Thompson
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Jamie
Guest
Guest
Sun Feb 14, 2010 10:03 pm
Ecnerwal wrote:
Quote:
In article <4b6f3677$0$20407$426a34cc_at_news.free.fr>,
OBones <obones_gfd__at__gfd_altern.org> wrote:
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Last I recall, the LM317 application notes include this circuit - all
you need is to pull the reference negative. Page 16 of the PDF, typical
applications, 0-30V regulator. LM317 datasheet is really LM117 datasheet
(they are a family). National Semi website or your favorite source of
datasheets.
If the supply for the reg isn't being used for anything else, you can
OBones <obones_gfd__at__gfd_altern.org> wrote:
Using a LM317, I can create an adjustable voltage supply without much
complexity, but it cannot go lower than 1.25V
Would you know some equivalent IC that would allow to go down to 0.001 volt?
It doesn't need to supply much more than 100mA but it would be nice if
it was thermally protected like the LM317.
Last I recall, the LM317 application notes include this circuit - all
you need is to pull the reference negative. Page 16 of the PDF, typical
applications, 0-30V regulator. LM317 datasheet is really LM117 datasheet
(they are a family). National Semi website or your favorite source of
datasheets.
If the supply for the reg isn't being used for anything else, you can
lift the (-) side via 2 SI diodes. On the other side of these diodes
then becomes your common (-) to every thing else..
The drop maybe a little more than needed thus giving you a little
(-) voltage out when setting the level to 0 how ever, one can simply
use an internal pot on the low side of the external pot to prevent any
less than 0.
This is all nice and rosy how ever, you will lose the amount of
voltage at the top that you shift at the bottom. If this isn't going to
be an issue, then you're all set..
(- side of supply)-----|<---|<------( this now becomes the COM to the
reg and and out side world)
some people use ZENERS to pull this trick off when needing some (-)
voltage
elektroda.net NewsGroups Forum Index - Electronics Design - Adjustable voltage source from 0 to 12V
