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 ReidCommented Feb 23, 2015 at 20:36
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1 Answer
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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.
answered Feb 24, 2015 at 0:45
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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\$ Commented Feb 24, 2015 at 1:09