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Split power supply with 7815 and 7915

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hummusdude:
I’m using a 7815 and 7915 for a split power supply for some TL072 op amps that are part of an audio pre-amp and also a Baxandall tone circuit that also uses a TL072. I know I don't need so much voltage for these circuits, but the reason I'm using the 15V supply is because I'm tapping the DC voltage from the power amp power supply and it puts out 25VDC. Not sure if it makes a difference but I'm hoping that by using a 15V regulator instead of a 5V regulator it will reduce power dissipation and excess heat on the 7815/7915. Does that make sense?

The data sheet for the 7815 has a few different sample application circuits. One is called a “fixed-output regulator” and uses only a couple of caps for the power pins as usual. Another sample circuit is called a “split-power supply” and shows a 7815 and 7915 used together, along with some diodes and extras caps, to form dual output dc power supply for an op amp.

My question is, is there an advantage to using the split-power supply design over using a separate 7815 and 7819 in a fixed-output regulator setup to create the positive and negative power rails for the op amps? The split-power supply design uses more parts, but I’m already using a 7815 and a 7819 in the fixed-output regulator set up on the breadboard to provide power to my op amps and it seems to be working fine.

Appreciate any feedback!

bob91343:
I don't get it - from your beginning description I thought you were using the dual arrangement.  It should work okay.

And yes, the higher voltage regulator dissipates less heat, even with the same load current.  But you raised the load current by running the amplifiers on a higher voltage.  So I guess it depends.

hummusdude:
Sorry... I meant that I'm using a 7815 and a 7915 in the fixed output regulator configuration. Each has a couple of stabilizing caps on the power pins as the datasheet recommends. But the data sheet also shows a different configuration called a "split-power supply", also with a 7815 and a 7915, but with a couple of diodes and some extra caps. I'm wondering if there's an advantage to using the split-power supply setup instead of just using a 7815 and a 7915 separately, as it shows in the diagram I attached.

ledtester:
Except for the diodes, there is no difference between the "split-supply" schematic and the recommended circuit diagrams for the 7815 and 7915.

From the 7915 datasheet, the recommended caps are 2.2uF on the input and 1uf on the output.

From the 7815 datasheet the recommended caps are 0.22uF on the input and 0.1uF in the output (if needed).

The diodes are there to give a form of reverse polarity protection -- e.g. if you use it to charge a battery and you accidently connect the battery the wrong way around. You can omit them if you don't need this protection.

See the following comments about the diodes.

hummusdude:
Ah...that makes sense now that you explain it. Thanks!!

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