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| What's DIAC? |
| | The diac is a bidirectional trigger diode which is designed specifically to trigger
a triac or SCR. Basically the diac does not conduct (except for a small leakage
current) until the breakover voltage is reached. At that point the diac goes into
avalanche conduction also at that point the device exhibits a negative resistance
characteristic, and the voltage drop across the diac snaps back, typically about 5
volts, creating a breakover current sufficient to trigger a triac or SCR |
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| What's SIDAC? |
| | SIDAC is a silicon bilateral voltage triggered switch with greater power handling
capabilities than standard DIACs. Upon application of a voltage exceeding the SIDAC
breakover voltage point, the SIDAC switches on through a negative resistance region to a
low on-state voltage. Conduction will continue until the current is interrupted or drops
below the minimum holding current of the device. |
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| What's ESD Protector? |
| | ESD in this context is a high-voltage transient with fast rise time and fast decay
time. Several thousand volts of ESD with a high rise time (dv/dt) could break through
the junction layer of protective devices easily and cause damage. ESD surge energy,
however, is very small, and it does not require much energy-handling capability from
a protective device. Electrical overstress (EOS) is a much slower phenomenon than
ESD. Therefore, the following factors should be considered when designing for EOS
and ESD protection:
1. Voltage-clamping devices should limit the surge voltage to a safe level for the
circuit or component being protected.
2. Voltage-clamping devices should withstand several thousand volts of a fast
dv/dt impulse.
3. Protective devices should be small enough to fit into a limited space on a
printed circuit board (PCB). Most components that require ESD protection are
small surface-mount devices (SMD).
4. Current-limiting devices are sometimes not effective for ESD protection because
ESD current is very small and does not induce much voltage across the device.
5. Limiting devices with high impedance are not effective for ESD protection. The
stray capacitance in these devices could provide low reactance. |
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