Differential Power Supply?

Is this the type of thing you are looking for?

Try seaching 'dc dc power converter'.

"Bipolar output dc-dc converter" is a good search term. "dual output dc-dc converter" also works.

Digi-Key carries a wide range of converters. 236,352 search results on their site alone.

Happy shopping!

Hi Mikerho,

Just something to be aware of when using dc-dc converters: internally they are a type of switched-mode power supply and as such are inherently noisy. Depending on your application and the specific converter used, this could pose a problem (or not). If it does, you may find the following links helpful in mitigating the noise:

DC-TO-DC CONVERTER NOISE REDUCTION

Method to Reduce the Output Ripple & Noise of Power Supplies

Minimizing Noise Generated by Switched-Mode Power Supplies

-AW

I have a dual TRACKING power supply circuit.

It's the reason why Edison was slapped by Tesla, right in his face.

Huh?

Tesla was a genius finding out the AC thing. You can not just step down or up voltage in DC without compromise. You need to lose some energy to step down or up the voltage in DC. Makes it hard, costly and inconvenience in transmitting power, while in AC its simple adjustment like how the variac is constructed.

That is not totally accurate.

Transformers have some power loss as well, so some energy is wasted always. AC power is good for transmission, but it is not always the best solution.

For low voltage applications (up to 3kV) it might be interesting to transmit power using SMPS, due to the reduction on the size of the converter because the frequency is incremented. Moreover, copper (and iron) is way more expensive than Silicon semiconductors.

Nikola Tesla solved the problem for long distance transmission of the power, but we are a century ahead. Technology has improved a lot since then.

Here is what you need to know. The solution will depend mostly on the power you want to draw from the supply, and if you need the outputs to be isolated.

1. For very low power you can use a solution with Switched Capacitors, like LMC7660
2. For a medium power, you would need a more common SMPS (Switch Mode Power Supply).
1. Çuk converter for the negative output, and Buck or boost if your positive output is different form your positive input, Buck to step down, boost to step up. That would be if you do not need an Isolated Output.
2. For galvanic isolation I would use a Push Pull for low voltage, Half Brige Medium Voltage, Full Bridge for High Voltage Topology for high efficiency and power (up to a few kilowatts), or Flyback if you do not mind sacrificing some efficiency (several watts applications). You need to get 2 isolates outputs, and connect the negative (-) of the first output to the positive (+) of the second output, and that same point must be resistor grounded.
3. Finally for high power, same topologies as before, but using IGBTs instead of MOSFETs.

If you are in a cool project I might be interested in designing it for you :P

PD: I forgot to mention the OPAMP power supply, I recently learned about in the EEVBLOG. Combine it with an isolated step up PSU and you will get the voltages that you need (still low voltage applications).

(this is a screenshot from Dave's whiteboard I keep in a safe place)

If you want simple, here is one:

If you need regulated voltage you can add positive and negative voltage regulators:

http://www.onsemi.com/pub_link/Collateral/LM337-D.PDF (negative)

http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF (positive)

The questing was for DC input. He probably want to power some portable device where the input is usually a Galvanic Cell.

And seriously, linear regulators for OPAMP supply? Linear regulators have an OPAMP inside, so it means using an OPAMP for powering another OPAMP. I would use just the first OPAMP and live with it.

The OP said the power source is a battery.

Then how about two batteries, each with ¹/₂ the voltage of the original one? Job done sticker.

Yeah, that works. I've used it myself and a few here have mentioned it, along with another technique of using a resistor divider across a battery and buffering the midpoint to make a virtual ground. Both techniques are fine for non-critical applications. These may work for the OP or they make not, depending on what his particular (and unstated) requirements are. Haven't heard back from him so no telling what these might be.

Ahem...you're "transforming", "full wave bridge rectifying", and filtering...everything associated with AC voltage.

He wants to start with DC.

While it is true that the simple circuit I posted in comment 3 would only be ueful for high impedence signals (obviously rail voltage would skew is one tried to draw power from such a circuit), it would be perfect for driving an inverting or non-inverting signal to an Operational Amplifier, which is what he asked for.

You probably would want to add capacitors between the supply busses and ground to provide a low impedance path for AC.

Unfortunately, in this circuit the 'ground' itself has a high impedance, namely 5 kΩ, and so the AC coming in through a low-impedance path would tend to 'wiggle' it. The ground could be improved considerably by buffering the midpoint. Some of the other comments mention this.

There are plenty of solutions around on google, look here:-

Dual OP AMP DC Input Power Supply

If your battery just happens to be twice the voltage you need, or slightly more, that is a 12 volt battery and you need plus/minus 5 volts for example, that would be great.

Here is a simple version taken from the above link:-

The link I provided, appears not to have been looked at by some here, but it provides circuit diagrams for many different input voltages, output voltages and currents.

Sadly, the OP has not provided this information up to now, which is the reason I provided so many different ways to possibly achieve his goal....

Also proving that what he needs is not difficult to achieve and could be easily attainable for under $10 including a suitable box!!

Worst case maybe $20!

No need to spend more, unless the need is for relatively high powers....

You connect two 9v batteries together to get +9v and -9v. This will only cots you $100.

Whilst dual-battery and battery+resistor-divider schemes are fine for many projects, we don't know the OP's actual requirements in a power supply. He may in fact need a tightly-regulated dual supply whose output voltages are constant over the bulk of the battery's life and neither of these two simpler schemes provide that. They may be fine for his app or they may not; we don't know.

Isn't that usually done by having the null of the op amp output on Vcc/2? That way 0 volt is effectively -Vcc...

OR, just bring two batteries, and hook one up backwards relative to ground (virtual ground is all you need anyway, unless you drive a stake through its heart).

I would draw you a picture, but I don't want to insult you. Try using a couple of Li+ ion battery packs from cordless drills that you can charge up ahead of time. Wire one up where convention + is +, and the other where convention + is Vgnd. That way the negative terminal on that one is negative.