1.235 V fixed shunt reference for bias and comparison circuits
The LM385LP-1-2 is a fixed 1.235 V shunt voltage reference from Texas Instruments, in the TO-92-3 through-hole package. It is part of the LM385 family, designed for low-power bias, comparator thresholds, and ADC/DAC reference duties where a stable 1.235 V rail is needed. The shunt architecture means it operates like a two-terminal Zener: a bias resistor from the supply sets the cathode current, and the part regulates the output voltage as long as the cathode current stays above 15 µA and below 20 mA.
Noise and drift — what the numbers mean for a calibration bench
For a 1.235 V reference, that is about 49 ppm rms — acceptable for general-purpose metrology but not for a 16-bit ADC's internal reference without averaging. The 20 ppm/°C temperature coefficient means the output shifts roughly 0.7 mV over the full 70 °C span. If your board sees a 30 °C rise above ambient, budget 0.74 mV of drift — within a 10-bit LSB at 1.235 V (1.2 mV) but tight for 12-bit.
Active production — sourcing and compliance
No official second-source or pin-compatible replacement is listed, but the LM385 family is widely cross-referenced in the industry.