The effective PN junction operating temperature for very low zener power levels and pulse test methods will approximate ambient temperature conditions. In such examples, zener voltage regulation versus temperature is only affected by the ambient temperature conditions. However, most zener JEDEC “1N” diode registration types identified in the industry are specified for zener voltage at dc thermal equilibrium conditions at a given test current and power. Their effective zener dc power and self heating effects will often generate sustained internal PN junction temperatures operating at 30°C or more above their case or lead temperatures. Test conditions for zener voltage are typically at 25% of full rated power.

For more information on Zener diodes, visit Microsemi’s Web site.