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I have a IRF540 power Mosfet driving a 12 volt motor. Currently I am using a 100 ohm gate input resistor, It is working fine. What I want is the maximum gate resistor value that I can use and still drive it properly with 8 Volts DC, This does not need to be an exact value just some approximation will do. In most case this is a steady state voltage so timing is not a real consideration. The only reason for this is if the IRF540 shorts out, I do not want it to take out the driver IC as well. I know about heat sinking and current protection circuits but sometimes this still happens.

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  • \$\begingroup\$ Can you increase your gate voltage to 10V minimum? Datasheet says that 8V is at the bare edge of the FET being fully-enhanced. \$\endgroup\$ – Dwayne Reid Feb 23 '15 at 20:36
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The IRF540's maximum specified Gate leakage is 100nA at 25°c, so theoretically you could use up to 1 Meg (for voltage drop of 0.1V or less). However leakage current increases with temperature, and such a high resistance could make the Gate quite sensitive to noise.

Use the lowest value that meets your safety requirements. Anything up to 10k should be fine.

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  • \$\begingroup\$ Thank you for your answer I was thinking of 470 ohms so I am way under the maximum you have given me. Just wanted to be sure I was driving it well. I have done experiments increasing the gate voltage until the drain voltage changed no more and found 8 volts met this requirement. \$\endgroup\$ – user66377 Feb 24 '15 at 1:09

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