The NTE999 is a three–terminal adjustable shunt regulator with guaranteed thermal stability over a temperature range of –0° to +70°C. The output voltage may be set to any value between Vref (approximately 2.5V) and 36V with two external resistors. This device has a typical dynamic output impedance of 0.2Ω. Active output circuitry provides a very sharp turn–on characteristic, making the NTE999 an excellent replacement for zener diodes in many applications.
 
Full spec sheet:
https://www.nteinc.com/specs/900to999/pdf/nte999.pdf