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The most common modern type of varistor is the metal-oxide varistor (MOV). This type contains a ceramic mass of zinc oxide (ZnO) grains, in a matrix of other metal oxides, such as small amounts of bismuth, cobalt, manganese oxides, sandwiched between two metal plates, which constitute the electrodes of the device.
Metal oxide varistors typically have lower resistance as they heat up; if connected directly across a power bus, for protection against voltage spikes, a varistor with a lowered trigger voltage can slide into catastrophic thermal runaway and sometimes a small explosion or fire. [23]
The strict physics definition treats passive components as ones that cannot supply energy themselves, whereas a battery would be seen as an active component since it truly acts as a source of energy. However, electronic engineers who perform circuit analysis use a more restrictive definition of passivity .
MOS stands for metal-oxide-semiconductor, reflecting the way MOS-transistors were originally constructed, predominantly before the 1970s, with gates of metal, typically aluminium. Since around 1970, however, most MOS circuits have used self-aligned gates made of polycrystalline silicon , a technology first developed by Federico Faggin at ...
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Although this standard is designed for testing equipment as a whole at system level, not for individual protection devices, in practice this surge waveform is often also used for rating Transient Voltage Suppressors (TVS), Gas Discharge Tubes (GDT), Metal Oxide Varistors (MOV), and other surge protection devices.
Three-layer DIAC. The DIAC (diode for alternating current) is a diode that conducts electrical current only after its breakover voltage, V BO, has been reached momentarily.. Three, four, and five layer structures may be us
3) If varistors are not designed for lightning protection, then why do varistor datasheets routinely specify numbers unique to lightning strikes (ie 8/20 microsecond pulses)? Varistors are for protection from lightning strikes and from other similar and lesser current pulses. But varistors are only one component of the application device.