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Forum Index : Electronics : mosfet gate question

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Murphy's friend

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Joined: 04/10/2019
Location: Australia
Posts: 671

Posted: 04:47am 04 Oct 2023

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I want to connect two identical mosfets in parallel.

The usual way is to have a separate gate resistor to each gate from the driver output.

Is there a disadvantage when connecting the two gates together and have just a single gate resistor from the driver to that connection?

Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1151

Posted: 07:55am 04 Oct 2023

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Murphy's friend said ... Is there a disadvantage when connecting the two gates together and have just a single gate resistor from the driver to that connection?

Yes and depends, its not best practice to common them together driven via a single resistor. Individual Mosfets have an inherent input gate impedance that is different to some degree between batches; using individual gate resistors evens out any impedance mismatch.

For fast high power switching applications and you want current sharing, having a single common resistor means the mosfet with the lowest input impedance will hog the drive current and turn on first, it may blow up if it is not rated for the full current, while the others are yet to turn on; then they may cascade self destruct also.

For slow transition drive eg driven from a high Z current source, you can common the gates to a single resistor or leave it out.

Cheers
Mike

Murphy's friend

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Joined: 04/10/2019
Location: Australia
Posts: 671

Posted: 09:48am 04 Oct 2023

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Thanks Mike, I won't risk it then. Its for that SMD mosfet inverter I'm building.

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