Dual PSU Question

[dano12]

Given this:



The first one shows the power supply I use most often. R1, C1, and C3 filter the supply, while D1 provides polarity protection. It works, I'm happy and life is good.

Now the second one where I'm creating a bi-polar/virtual ground power supply, two questions:

To duplicate the 100ohm part of the filter from the first one, would I just used two 100ohm parts, one on each leg out of the power source?

Reverse polarity: I assume my diode goes across the rails, just like in the first version?

I think I have it right, but I'm still quite the noob.

[Cliff Schecht]

Unless you are getting your "DC" from a full-wave rectifier, your schematic won't work. In order to make that virtual ground, you need to be able to sink current both ways. If you have an AC source, then the PAiA method works the best. Take a look at the links below, it should help you out:
+



Full-wave rectifier:
http://www.paia.com/KRUKits/K83/K83_schem.jpg

Half-wave rectifier (upper-left hand corner - I think this is what you're looking for):
http://www.paia.com/manuals/docs/9305-tubehead-schematic.pdf

[sean k]

Or you use two 9V batteries and ground them in the middle or alternately 6 x 1.5V cells and ground the centre where the first three meet the next three...  (V+)+ 1.5 - + 1.5 - + 1.5 - ground + 1.5 - + 1.5 - + 1.5 - (V-)

[Cliff Schecht]

Or you use two 9V batteries and ground them in the middle or alternately 6 x 1.5V cells and ground the centre where the first three meet the next three...  (V+)+ 1.5 - + 1.5 - + 1.5 - ground + 1.5 - + 1.5 - + 1.5 - (V-)

Yeah those always work too. The only reason I posted what I did is because the 2nd image dano posted only shows a single DC supply. You need to be able to sink current on the positive rail and source current on the negative rail (I think that's right, positive DC current flows into ground and negative flows out of ground), which is impossible with a single voltage/current source.

[dano12]

Sorry, I thought it was clear on the schematic I am using DC.

Given the two schematics, assume a battery or some other DC source.

It does work fine actually.

My question was specifically about where to put small value resistors to form a filter.