negative 10V power supply

[Mizutsuki Raki]

To start with, I need negative 10V power supply for my MCS-4/40 tester (half done)
I can make this voltage by many method(like linear transformer, SMPS...) but I hope to make this with minimum chips for test.
Resultingly, intel 4004 needs 15V, so I think I can use 7810 and 7815 to generate them. And rename them. GND to negative 10V, 7810's 10V to GND, and 7815's 15V to 5V.

http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=4721
He used lab PSU. And I'm wondering if it is possible.

Thanks!

[magictom]

[Mizutsuki Raki]

I'm also considering the linear power supply. Connecting the 7805 to positive, and 7910 to negative.

[gekaufman]

Actually the 7810/7815 should work fine, as you'd be using the +10 supply as an effective GND.

- Gary

[berni]

It's no good idea to use a positive voltage regulator for a negative voltage.
You want a regulated negative voltage and not a regulated ground on top of an unregulated negative voltage.

When designing a dual supply with positive and negative voltages, you need to stick with the 78xx and 79xx combination, otherwise regulation will be poor or unpredictible.

Think also about some simple switchers. They come in positive and negative or even in an inverting versions...

[aberco]

It's perfectly fine to use a 78xx for negative voltage generation. The GND is defined only by the position where you want it. It has been done and proven for a very long time (and is even described in datasheets).