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Difference between SSR and Power MOS FET

FAQ No. FAQ02243

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Question

What is the difference between an Solid-state Relay and a power MOS FET?

Answer

There are two main differences between Solid-state Relays and power MOS FETs.

Difference 1:

There are DC Solid-state Relays and AC Solid-state Relays.

A Power MOS FET Relay can be used with either a DC load or AC load.

Difference 2:

The leakage current is smaller compared with an Solid-state Relay.

Solid-state Relay:

Leakage current causes the lamp to light dimly. A bleeder resistor is added to prevent this. The Solid-state Relay requires a snubber circuit to protect the output elements. This is the cause of Leakage current.

Power MOS FET Relays:

Because the leakage current is very small (e.g., 10 mA max.) the lamp does not light dimly. This is because a snubber circuit is not required to protect the output element MOS FET. A varistor is used to protect the MOS FET.

The circuit can be simplified and work reduced because a bleeder resistor is not required.