Electrical – How to make a split-supply from a single supply by using two linear regulators like LM7812 & LM7912

power supplysplit

I want to obtain +-12VDC supply from a 24VDC supply where the total load will driver 100mA max. I tried using two power supplies but one of them blew up. I need the split supply for excitation voltage which I mentioned in my previous question. So I decided to make a spit supply from a 24VDC supply. I have some many LM7812, LM7912 or equivalent. I tried the following circuit:

Schematic using LM7812 and LM7912 with common ground

But instead of +-12VDC I'm getting the following output:

Voltage output on the scope

These are the only components I have at the moment.How can I use them in a way to obtain +-12VDC?

edit:

Regarding @Trveor's answer:

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edit2:

Discrete solution(?):

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Best Answer

If the 24V supply is isolated use a virtual ground instead..

Something like this..

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Choose an op-amp capable of sourcing and sinking the currents you need. You may need to heat-sink the op-amp if currents are large.

RE ISOLATION Note the drawing below, both power supplies have their negative outputs ties to mains ground. When wired up this effectively shorts the output of the virtual rail to the negative terminals. As such you need to be sure things are correctly isolated in your circuit and internal to the supply. BTW: Some supplies have a jumper on the terminals that needs to be removed.

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