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I am trying to use an TI UA741 opamp and supply it with +12 VDC and -12 VDC. To obtain -12 VDC, i configure the power supply like i have shown below on the picture. Can i get -12 VDC (V2 on Figure 1 that i connected the circuit without any regulator)using this configuration in real life? I am also using a negative voltage regulator L7912CV. I have shown how i intented to design with regulator in Figure 2 that i have roughly shown without peripheral resistors or capacitors. If you share your comments i will be happy. You can advise any other methods to achieve negative voltage. I am just trying to clutch the logic. Thank you.

Figure 1:

enter image description here

Figure 2:

enter image description here

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  • \$\begingroup\$ Where is the GND connection of the 7912? \$\endgroup\$ – Batuu Jul 19 '17 at 14:54
  • \$\begingroup\$ It will be connected to circuit's ground, i just visualized what i want to do roughly. \$\endgroup\$ – layout789 Jul 19 '17 at 14:57
  • \$\begingroup\$ I don't recognize the pin out on the 8 pin device shown in yellow on your 2nd circuit. \$\endgroup\$ – Andy aka Jul 19 '17 at 14:59
  • \$\begingroup\$ Pin numbers are not important i have updated the picture. \$\endgroup\$ – layout789 Jul 19 '17 at 15:10
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    \$\begingroup\$ If your design is meant to solve a real problem (not an academic exercise) please read Reasons not to use a 741 op-amp? before you continue. \$\endgroup\$ – The Photon Jul 19 '17 at 16:03
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Theoretically that will work, but only if V2 is a floating (isolated) supply. Many power supplies are actually referenced to the protective earth AKA 3rd prong. These would not obviously work.

For an easy way to generate -12V from +12V, you can use a buck-boost SMPS circuit. TI SLYT286 shows how to use a common buck-converter in an inverting buck-boost configuration. Do note that this will effectively double the voltage so you need something that's OK with 24VDC input. You can obviously use a dedicated buck-boost converter but for actual product designs it's beneficial to use same parts if you can.

http://www.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slyt286&docCategoryId=1&familyId=751&keyMatch=SLYT286&tisearch=Search-EN-Everything

If you really want to get fancy, you can do +/- output SMPS circuit using a common mode choke but that's a bit beyond the scope here.

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