The PCB has two sets of bipolar power rails at 3.3 V and 12 V. The 3.3 V rails are powered by the Teensy's built-in 3.3 V supply (which in turn is powered via the USB connection), using a TC7660 inverting charge pump IC on the PCB to feed the -3.3 V rail. The 12 V rails are derived from an external 24 V unipolar supply, using a resistive divider with its midpoint connected to the ground of the 3.3 V unipolar supply. The Teensy microcontroller and the (single-supply) MCP602 dual op-amp IC used in S1 and LP1 are operated at +3.3 V. The OP827 op-amp in the DC compensation circuit is operated at 12 V, and the OPT101 amplified photodiode is powered using a combination of the +12 V and -3.3V rails to allow for bipolar operation around 0 V.