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I'm looking to drive an active magnetic 3V buzzer with an ESP32 pin through an N-Channel MOSFET as follows:

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I'm not sure if the 100 Ohm resistor is needed and whether the value is correct. Buzzer datasheet says 50mA max current but in their sample circuit they don't use any resistor at all.

My MOSFET has near-0 resistance and buzzer's resistance is 16 Ohm. Since I want to use a resistor from JLCPCB basic parts library, I'm limited to 100mW / 100 Ohm = 30mA since at 68 Ohm I'd be over the 100mW on the resistor. Is this reasoning sound? :) Thank you.

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When driving the buzzer modules you don't need any series resistors as long as the supply voltage is within the range given in the datasheet.

What you see as "50 mA" is the "consumption" i.e. the current it draws from the supply to meet the specs it has (SPL, frequency, etc). And 3V buzzers are generally happy to be driven even with 3.3V. So you don't need a series resistor at all.

It's good to keep the protection diode across the module though, as the module and the layout (potentially) contain inductive elements which can potentially generate high voltages across the driving switch (MOSFET or BJT) enough to kill it.

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