What is it?

We call this device a rail splitter. It's takes a single-output power supply (a single rail) and forms "split rails" (positive and negative, centered around a common ground). This is useful for powering many analog circuits, especially op-amp circuits. It also features common-mode filtering, which we've found to be the main cause of unwanted noise coming from switching bench-top power supplies.

Why did you make it?

When powering up a circuit on the bench that uses split rails, you usually need two floating power supply outputs connected in series. But if you only have one available power supply output, you need some device/circuit that can split the single rail into positive and negative rails. You also need both rails to maintain a stable voltage with-respect-to the common ground even if the current drawn from each rail is not equal. This is where a device like the Rail Splitter comes in handy.

Let's say we have a 30V power supply. The rail splitter will turn this into +15V and -15V centered around a common ground (0V). Even if you draw more current out of the +15V rail than you flow into the -15V rail (or vice-versa), the voltages will be maintained precisely. In fact, our Rail Splitter can maintain 100mA of imbalance with a 30V input. At lower voltages, it can maintain higher imbalances.

What makes it special?

In a cursory search on the internet, we didn't find much in the way of devices that did exactly this. The ones that do exist seem to handle a lower current imbalance between the two rails. So we decided to make our own!