Ultra-low noise, bi-polar, programmable current sources

We present the design process and implementation of fully open-source, ultra-low noise programmable current source systems in two configurations. Although originally designed as coil drivers for Optically Pumped Magnetometers (OPMs), the device specifications make them potentially useful in a range of applications. The devices feature a bi-directional current range of $\pm$~10~mA and $\pm$~250~mA respectively on three independent channels with 16-bit resolution. Both devices feature narrow 1/f noise bandwidth of 1~Hz, enabling magnetic field manipulation for high-performance OPMs. They exhibit low noise of 146.3~pA/$\sqrt{\mathrm{Hz}}$ and 4114~pA/$\sqrt{\mathrm{Hz}}$ which translates to 14.57~ppb/$\sqrt{\mathrm{Hz}}$ and 16.46~ppb/$\sqrt{\mathrm{Hz}}$ noise relative to full scale.