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To power an op-amp with a dual supply (+Vcc and -Vcc) you can use two power supplies connected in series.

I would like to find an alternative and less expensive way to do this as (in my project) the two power supplies would only power the op-amp which seems a bit wasteful.

circuit_series

I tried to buy two cheap non-isolated LM2596S DC-DC converters on the internet and connect them in series (to get +12 V and -12 V, total 24 V), but they don't work properly (perhaps due to the non-isolated feature).

LM2596S_series

In other questions isolated DC-DC were used and with some connections it was possible to make them work in series, having a +Vout and a -Vout (in detail).

Also, excuse the question, for example this isolated DC-DC converter has a (dual) output of +/- 12 V. Does that mean that the total output voltage is 24 V (between +Vo and -Vo pins), or can I only have +12 V or -12 V?

I need a dual power supply for the two op-amp (TL081), which are part of precision full-wave rectifier circuit.

full-wave-prec-rect

Could there be other (preferably cheap) ways to achieve this without having two power supplies?

Please, could I ask you to post a drawing of your solution?

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    \$\begingroup\$ It depends on many things which option is the simplest. Often a virtual ground works out well. Show your circuit! With your approach at least one isolated converter is needed. But if there is only one opamp needing split supply with a few mA even charge pumps can do it. There are many. Show your circuit as is ;-) \$\endgroup\$
    – datenheim
    Feb 11, 2023 at 11:30
  • \$\begingroup\$ tracopower.com/int/dc-dc-converters or others manufacturers \$\endgroup\$
    – Antonio51
    Feb 11, 2023 at 15:26
  • \$\begingroup\$ philfs, I agree with @datenheim about needing to know your current compliance requirements. If it isn't a lot, then simpler/cheaper/smaller techniques can be used. It also looks as though you want to avoid wiring up complex circuits, noting that you are using two COTS DC/DC boards (which cannot be connected as you show) rather than designing and building them. If you aren't into the idea of designing and building from scratch, then you should just buy a dual supply. I bought some surplus wallwart types for USD5 that provide +/-12V @ 1A, and +5V @ 3A, running the power out to a DIN connector. \$\endgroup\$ Feb 11, 2023 at 18:04
  • \$\begingroup\$ Edited with circuit where 2 op-amps need a dual supply to work. Please excuse me. \$\endgroup\$
    – philfs
    Feb 11, 2023 at 19:12
  • \$\begingroup\$ @philfs Yes, this converter you now mentioned will do the job basically. There are far more types in similar form with 0.5...3 W power, also as dual 15 V. You must not even use isolated converters. Don't choose more W than required (bad efficiency) - two TL071 don't need much. You can tie GND of input and output together on isolated types or choose non-isolated types (cheaper). You may need to add a bit filtering to get their ripples down. Higher switching frequency may be easier to filter. Some require a minimum load, so inspect the datasheet. \$\endgroup\$
    – datenheim
    Feb 11, 2023 at 23:08

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Simply putting two power supplies in serial can't make stable dual output. Dual-mode power supplies are often designed as "tracking" converters.

Here's one of the option I used before. It's ±5 V, not ±12 V as you need, but you could find similar ±12 V regulators. As op-amp power consumption was small and I needed 5 V, this was enough for me.

TPS65133 costs ~$2.

enter image description here

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  • \$\begingroup\$ Excuse me if I ask you but I want to understand it properly (about dual supply), this IC gives voltage +/- 5 V, so the final voltage should be 10 V? \$\endgroup\$
    – philfs
    Feb 11, 2023 at 18:53
  • \$\begingroup\$ @philfs You probably want the higher voltage version: ti.com/product/TPS65130 But yes, you get -12v, 0V, and +12v (or whatever voltage you choose) for powering opamps or similar. \$\endgroup\$ Feb 11, 2023 at 20:16

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