AVR-L Voltage Protection Chip Varistors TDK AVR-L Voltage Protection Chip Varistors have no polarity due to symmetrical current-voltage characteristics equivalent to Zener diodes. The AVR-L Varistors offer exceptional electrostatic absorption capability with a response equal to, or better than, Zener diodes. These varistors maintain symmetrical current-voltage characteristics (even after electrostatic absorption) and are available in a 6.8V to 90V range.