Silicon planar zener diode. 0.5 W. zener voltage range Vznom = 130 V, Izt = 1 mA for Vzt . Silicon planar zener diode. 0.5 W. zener voltage range Vznom = 150 V, Izt = 1 mA for Vzt . 0.5W SILICON PLANAR zener diodeS 25 A standard and Snubberless" triacs Silicon planar zener diode. 0.5 W. zener voltage range Vznom = 200 V, Izt = 1 mA for Vzt .