It operates as a two-terminal Zener-like device: a series resistor biases the cathode current above 55 µA, and the reference regulates the output voltage between 1.24 V and 5.3 V. The ±1% tolerance on the output voltage is the key differentiator here — the standard LM385Z carries a looser ±3% tolerance, so this B-grade variant is the one to specify when the ADC reference or comparator threshold needs tighter absolute accuracy without moving to a more expensive series reference.
Output current and cathode current — sizing the bias resistor
The LM385BZ/NOPB can source or sink up to 20 mA of output current, which is enough to bias an op-amp input stage or pull up an open-drain comparator. The minimum cathode current is 55 µA — below that the reference drops out of regulation. When you size the series resistor from the supply rail, you need to ensure the cathode current stays above 55 µA under all load conditions. At light loads, the excess current just flows through the shunt, so the resistor value is a trade-off between power dissipation and regulation headroom. For a 5 V rail and a 2.5 V output, a 1 kΩ resistor gives about 2.5 mA cathode current — plenty of margin.
Temperature coefficient and noise — bench-level expectations
That is fine for general-purpose biasing and threshold setting, but not for precision measurement without calibration. The noise spec is 50 µVrms over the 10 Hz to 10 kHz bandwidth — low enough for most 8-bit and 10-bit ADC references, though a dedicated low-noise reference would be better for 12-bit or higher systems.
Package and mounting — through-hole legacy, still widely used
The TO-92-3 package (TO-226-3, TO-92-3 (TO-226AA)) is a three-lead through-hole transistor-style package. It is a standard footprint for breadboard prototyping, point-to-point wiring, and retrofit repairs on older PCBs. The supplier device package is TO-92-3. The mounting type is through-hole, so it is not a candidate for high-density SMT assembly, but it is easy to hand-solder and replace in the field. The shipping form is Bulk — loose parts in a bag, not tape-and-reel, which matters for pick-and-place volume.
The /NOPB suffix indicates RoHS3 compliance and lead-free construction, so it meets the EU RoHS directive and is suitable for new designs requiring lead-free soldering.