An electrical device such as this requires reverse leakage current of 100nA @ 15V.During operation, the maximum voltage - Zener (Nom) is reduced to 20V volts.As soon as the maximum voltage - Forward (Vf) is supplied, it reaches 1.3V @ 100mA V.
BZX55C20 Features
reverse leakage current of 100nA @ 15V 100nA @ 15V is the maximum voltage (Tol)
BZX55C20 Applications
There are a lot of Rochester Electronics, LLC BZX55C20 applications of zener single diodes.