Metal oxide varistor
Apr 23, 2021
The most common varistor is a metal oxide varistor (MOV, Metal Oxide Varistor), which consists of a ceramic block composed of zinc oxide particles and a small amount of other metal oxides or polymers, sandwiched between two metal sheets.
A diode effect is formed at the junction of particles and adjacent oxides. Due to a large number of messy particles, it is equivalent to a large number of back-connected diodes. At low voltage, there is only a small reverse leakage current. When encountering high voltage, the diode Reverse collapse occurs due to hot electrons and tunneling effect, and a large current flows.
Therefore, the current-voltage characteristic curve of a varistor is highly non-linear: high resistance at low voltage and low resistance at high voltage.
