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diode alternating current switch (component) (DIAC)

The DIAC(Diode Alternating Current Switch) is a bidirectional semiconductor switch for switching low currents. It is a three- layer diode, usually pnp, with one pn junction and one np junction. One of the two pn/np junctions is always operated in the forward direction, the other in the reverse direction.

The diac is high impedance when not switched, and low impedance when switched. It operates bidirectionally, equally in both directions, and switches when the breakdown voltage is exceeded.

Switching sign and characteristic curve of the diac

Switching sign and characteristic curve of the diac

Switching is triggered by applying a voltage. If the applied voltage exceeds the breakdown voltage, then the junction operated in the reverse direction switches to its low resistance state, making both junctions conductive. If the applied voltage is reduced and falls below the hold voltage, then one of the two layers flips to its reverse state and the diac is high impedance.

The voltage and current values are over a hundred volts and a few amps.

Englisch: diode alternating current switch (component) - DIAC
Updated at: 17.11.2019
#Words: 159
Links: bidirectional (BiDi), semiconductor, switch, layer, diode
Translations: DE

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