Fixed 2.5 V shunt reference in an 8-SOIC
The Texas Instruments LM385BDE4-2-5 is a two-terminal shunt voltage reference delivering a fixed 2.5 V output with ±1.5% initial tolerance. The shunt topology means it behaves like a Zener diode — no external bypass capacitor is required for stability, and the cathode current can range from 20 µA (minimum to maintain regulation) up to 20 mA (maximum continuous output).
The 2.5 V output is the reference voltage for the entire circuit — a load pulling more than 20 mA will pull the output out of regulation, so this part is suited for biasing op-amp inputs, ADC references with low sampling rates, or comparator thresholds, not for powering a rail. The 20 µA minimum cathode current means the series resistor from the supply must be sized to deliver at least that much current at the lowest supply voltage; otherwise the reference drops out. Noise is 120 µVrms integrated from 10 Hz to 10 kHz; for a 10-bit ADC with a 2.5 V reference, that noise contributes less than 0.2 LSB, but for a 16-bit system it may need post-filtering.
Package and rework reality
Pin 1 is clearly marked by a bevel on the package corner; orientation is unambiguous under a loupe.
It is ROHS3 compliant, so no exemption paperwork is needed for EU or global shipments. The base product number is LM385, and the suffix BDE4-2-5 denotes the ±1.5% tolerance grade, 2.5 V output, and the 8-SOIC package in tube format.