I have a small DAC application where I need to generate +/- 10V swing using a MCP4725 DAC. The required conversion of the unipolar 5V max out of the DAC needs to be converted into a bipolar signal. There is a application note from Analog Devices using OPA188 opamp for this.
Now I am looking for a power supply circuit that can take in a 24V dc supply and convert to a bipolar +/-12 V supply to power the Op Amp. Any simple circuit for this ? ( Google mostly brings up the center tap transformer type with 7812 / 7912 regulators. )
They make power supplies that give both + and - outputs. Look for: Power Module Buck Step Down Converter Isolated DC-DC. That would allow you to use a inexpensive 12V power supply.
OR, bias a current draw greater than the expected load. I was offering an easy solution. There are always compromises. My suggestion, is a single device low cost and low noise , compared with most switching regulator solution options.
I like the 7912 upside down configuration--Most of the logic and control will be on the GND to +12 side and the GND to -12V side will typically have less stringent requirements.
I manufacture a device that includes a bipolar 12-bit 4-quadrant Multiplying DAC. I use these to convert the incoming 24V to +/-12 for the DAC and my opamps.
They are in short supply these days (what isn't?) so I'd grab whatever you need right away.
You can get isolated DC-DC converters. With the output isolated from the input you can ground the + output for a negative output-voltage. I use one for an op-amp in a car.
But in your situation you might just want to buy (or build) the "correct" power supply. I assume you don't need the 24V. I also have some power supplies that I bought that have +5V and +/-12V.
Sometimes the price is well worth the time saved. But OP will decide
Also, my general assumption when people come in here is that the grounds are common.
There are cheaper approaches like some of the old capacitor-based charge pump devices e.g., the ICL7662 if you don't need voltage regulation. You only need the device (costs about $1.00) and two capacitors and it will provide a ground-referenced negative voltage output.
I haven't had any issues with noise at all. I've been selling these devices to the same customer for about 4 years now and the accuracy is well within their spec. It bears mentioning in any case that this is for a machine control application and the existing power supplies are probably even dirtier than this DC-DC converter
Thanks to all those posted solutions. Have gone through and came up an idea. See the sketch below ... use two numbers of LM2596 buck convertors. Available on line for less 1 USD each. And these are capable of delivering more than an Amp though I dont need that much. Of course the 24V ground and the new ground cannot mix. Thats not an issue . Please confirm if this will work
The standard LM2596 modules I've seen are not isolated. They use an inductor not a transformer. Dual-output bipolar switch-mode supplies are standard components available off-the-shelf.
But its probably simpler cheaper to do the virtual ground thing with a spare opamp as mentioned.
Adding a class-B buffer as suggested in #19 is doable, but you will need to bias it properly to prevent oscillation - just using two transistors like that will destabilize the feedback loop and perform poorly. See the "practical class AB amplifier" circuit here: https://www.circuitstoday.com/class-b-power-amplifiers
