Can I drive a relay with a transistor?

Question:

Can I drive a relay with a transistor?

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Answer:

DC coil relays can be driven by transistors.

However, the back electromotive force generated by the coil when it’s turned off may cause damage to the semiconductor or device malfunction. As a countermeasure, add a surge-absorbing circuit to both ends of the coil.

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Explanation:

For more about protecting relay coils from surge, refer to FAQE10041“What are surge countermeasures in coil relays?” and Safty Precautions for All Relays: 2-2-5 Preventing Surges When the Coil Is Turned OFF.

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Quick tips:

If a surge-absorbing circuit is added, the relay release time will be longer. Check the circuit before use.

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