Is it legit to use DC source with voltage regulator to create dual power supply for op-amp?
If you're a little bit creative, and you don't mind the ground connection being non-standard, you can do this:







simulate this circuit &ndash; Schematic created using CircuitLab

The reason that the ground is non-standard on this is because a split supply is usually grounded at the center-tap (0V).  If your 24V supply is floating (not grounded), then you can still do this, but if the supply's negative output is permanently grounded, then you have to remember that what the 12-0-12 circuit calls its reference is actually 12V above ground.  That might make a difference for any outside-world connections you may have.

Also, this circuit as drawn requires that the negative side of the load draw at least a little bit more current than the positive side.  That's because the regulator can only work in one direction.  Or if the positive side is always loaded more, then you can "turn it upside down", so to speak, and use a negative regulator instead.



That said though, you're using this for op-amps.  They don't actually care about the center tap anyway.  All they actually see are the extremes that their power pins are connected to, and signals wiggling in relation to that.  The split rails are only specified as a matter of convenience.  So if all you need is a signal reference, and not an actual power rail, then you can do this:







simulate this circuit

Use a spare op-amp channel to buffer the voltage divider into something "stiff".  This allows the divider itself to use large values to save power.  You can use any value that you happen to have on hand; the only requirements to make it work are R1 = R2 and you're satisfied with their current draw.

You'll also notice that I've grounded the op-amp's output.  Yes, that's legal, provided that it's the only ground point.  (1)  Again, if your 24V supply's output is already grounded, then you have to use what it gives you and not add your own.



(1) In fact, I helped to repair my brother's bass guitar amp a few years ago, and the power amp itself actually did this!  What would normally be the output went to ground instead, and the speaker was driven between the input power transformer's center tap and ground.  Don't know why they would have done it that way, but it worked just fine.