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I have several voltages available and I need a -12v dc power for a DDS function generator.

The available powers I have are: 220v AC 15v DC 12vx2 DC 5v DC

Edit: I tried the method where I connect the two 12v supplies together, and I can get the -12v this way when I test, but once I plug the cable to the generator the adapter disconnects and I lose the -12v, acting like the adapter was shorted.

https://forum.digikey.com/t/get-a-positive-and-negative-voltage-output-from-power-supply/10593

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    \$\begingroup\$ necessary current, and: what output voltages must your DDS provide? DDSes are typically used to generate AC voltages, and well, you could work off a single supply and just AC couple the DDS output, shifitng it to the desired voltage range. Anyways, I'm sure such exist, but I've never seen a DDS that needs -12V: that seems excessive. \$\endgroup\$
    – Marcus Müller
    Commented Mar 24, 2022 at 18:33
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    \$\begingroup\$ your edit really answers none of the question we've asked! \$\endgroup\$
    – Marcus Müller
    Commented Mar 24, 2022 at 18:34
  • \$\begingroup\$ It is really frustrating, I think I made a mistake buying this generator and UI have to live with it. aliexpress.com/item/32794949155.html \$\endgroup\$
    – Shamooooot
    Commented Mar 24, 2022 at 18:35
  • \$\begingroup\$ that is useless without a datasheet, could you please link to the datasheet? \$\endgroup\$
    – Marcus Müller
    Commented Mar 24, 2022 at 18:35
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    \$\begingroup\$ Well, you can always just ignore that you've bought it and start doing something that actually fulfills your requirement (You might be able to reuse important parts!). Sadly, you've still not mentioned any of these requirements: which voltage ranges do you want to output? Which currents? \$\endgroup\$
    – Marcus Müller
    Commented Mar 24, 2022 at 18:38

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The way I usually do this is with a 78XX series DC DC converter, they can be wired to sink or source and provide positive or negative voltages. This is how to use a negative voltage from a positive one. Make sure you don't exceed the input to pin 3 voltage (32V for the P7812, which means you could use either 15V rails (27V span) or 12V rails (24V span)) They can also be paralleled (use small resistance or inductance between)

Here is a excerpt from the P7812 datasheet:

enter image description here
Source: https://www.cui.com/product/resource/p7805-s.pdf

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