# Make +6 and -6 and +3.6 and -3.6 volts from a 12 volt battery

We're working on a project that requires a stable +6 and -6 and +3.6 and -3.6 volts from a 12 volt battery. It has to be stable, even when the voltage of the source goes down. We came up with this:

But this doesn't work because the 6 volts aren't stable when the 12 volts drops. We can not use software in our project.

• Of course it does. You only have 12V of potential. Commented Jun 9, 2016 at 18:00
• Put a DC-DC step-up converter between the battery and your +/-6V. That will stabilise the input voltage to 12V if it drops. Commented Jun 9, 2016 at 18:17
• I'd also use two 3.6V precision references to your artificial ground to get your +/-3.6V - zeners don't make particularly stable voltage references. Commented Jun 9, 2016 at 18:18
• You forgot to mention how much current you will draw from those voltages. The opamp with the two 100 k resistors is a good choice as long as you only draw a few mA from the +/- 6 V lines. For the +/- 3.6 V I would use voltage regulators like LM317 and LM337, you can set their voltage with a couple of resistors. Commented Jun 9, 2016 at 18:41
• To get stable +/- 6 V from a varying 12 V you need something much more elaborate. I would use a boost converter to make 18 V. Then the 2 resistors + opamp to make that +/- 9 V. Then some LM317/LM337 regulators to make +/- 6 V from than and the same for making +/- 3.6 V from that. This is not the only way of course. Commented Jun 9, 2016 at 18:46