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help negative voltage

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japl

New Member
hi

what is the easiest way (small circuit) to produce a negative voltage for a op-amp -VEE. the input would be a positive voltage say +12V to -12V.

thnxs for the help
 

Nigel Goodwin

Super Moderator
Most Helpful Member
japl said:
hi

what is the easiest way (small circuit) to produce a negative voltage for a op-amp -VEE. the input would be a positive voltage say +12V to -12V.

thnxs for the help
Unfortunately, the ICL7660 is only rated at 10V, so that's prevents that been used :cry:

At a quick glance, I couldn't find a higher voltage version, but there may be one?.

Maxim give a design for doing this at http://www.maxim-ic.com/cookbook/powersupply/pdfs/+12to-12_500ma.pdf, but it looks rather complicated.
 

Styx

Active Member
just order in a DCDC converter. Newport do some very small (in size) dual output SIL modules.

Check out (these are british)
rswww.com
www.farnell.com

farnell deliver to the public, RS dont like to
 

k7elp60

Active Member
negative voltage

You could use a Linear Technology LT1054CN8 they are good to an input voltage of 15V. Digikey stocks them.
 

plot

New Member
i assume you are starting with a positive supply? if so, something along the lines of the following could be used... this creates a "floating ground"

of course, this contains an extra LED and Resistor to tell if it's powered, and the overall circuit will need to be slightly modified to accomidate 12 volts.
 

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Exo

Active Member
That will only work if the load draws equal amount of current on both the negative and positive side
 

bmcculla

New Member
Look for a charge pump IC. You should be able to find one that will give you a negative voltage equal to the positive voltage input.

plot - I don't think you can assume that OpAmps draw the same current from both rails. For example: an opamp driving 25mA into a load will be drawing those 25ma from the positive rail.

Brent
 
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