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gate resistance values

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mukeshp11

mukeshp11

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Dear All,

I want to calculate the exact values of teh on and off gate resistance for MOSFET irf840.

I see from data sheet for my vgs 15V i have 55nc of charge.
So i will get ig=Qc(charge)/Time to rise.

If i take rise time say 1us or something like that.
The i can find Rg as Vgs/Ig.

Similarly i have to go for ig during off and find out Roff resistor.

Am i correct in this case by following above equation.
or can somebody suggest some method better for selecting exact on and off values of gate resistors.


Regards
Mukeshh
 

The Gate behaves as a capacitor. If the frequency is higher you will need bigger current to charge and discharge the gate.Here is a good article on the subject.
 

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