Quad comparator for mixed-voltage industrial sensing
The Texas Instruments LM2901DG4 is a general-purpose quad comparator — four independent voltage comparators in a single 14-SOIC package. It compares two analog input voltages and drives an open-collector output low when the non-inverting input falls below the inverting input.
The supply range covers 2 V to 30 V for single-rail operation, or ±1 V to ±15 V with split supplies. That spans everything from a 3.3 V microcontroller rail to a 24 V industrial bus supply without needing a secondary regulator. Quiescent current maxes at 2.5 mA across all four comparators, so the power budget stays tight even on a 24 V rail — about 60 mW total at 24 V. Input bias current is 0.25 µA max at 5 V, which means you can use high-value feedback resistors (100 kΩ or more) without the bias current shifting the threshold more than a few millivolts.
Open-collector output — why it matters for level translation
The output stage is open-collector, compatible with CMOS, MOS, and TTL logic families. That means the output pull-up resistor connects to a separate supply — the comparator can run from 24 V while its output drives a 3.3 V FPGA input.