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Intrinsic Gate resistance of FQP9N90C MOSFET?

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treez

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Hi,

Do you know what is the RG value for the FQP9N90C MOSFET?
The datasheet does not say.
Presumably we have to work it out from the “turn on rise time” listed on page 2?

So, Ciss * R = 120ns
Therefore R = 120ns/Ciss = 57.1…it says the added R(gate) is 25 ohms, therefore, the intrinsic gate resistance must be 57.1 – 25 = 32 Ohms?

FQP9N90C datasheet:
www.onsemi.com/pub/Collateral/FQPF9N90C-D.pdf
 

A reasonable guess would be the Rg value from FQP9N90C Spice model, 1.6 ohms only.

The error of reasoning is in expecting switching time to be dominated by Rg which is hardly the case.
 
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See figure 13. Turn-ON rise time of the datasheet is the duration when Vds falls from 90% to 10%, and time constant of the input RC are not the same things.
 
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Hi,

I asume in your switching calculation you need to take Coss and the miller effect into account.
But I'm not sure about your test circuit and conditions.

Klaus
 
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I would reflect to the article post, at CMOS IC design it was a case, but with correct implant materials to the polysilicon gate nowadays pretty good RF MOS transistors are available. The article doesn't mention this fact, it was written like 12 years ago. For discrete devices probably the gate resistance not the case either.
 
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