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Intrinsic Gate resistance of FQP9N90C MOSFET?

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ocset:
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

ogden:
DC resistance shall be calculated out of Gate-Body Leakage Current using Ohms Law: 100 nA @ Vgs = 30V

In case you are looking for reactance, you may want to read following or other similar appnotes lying around internet:
https://www.vishay.com/docs/73217/an608a.pdf

ocset:
Thanks, but the intrinsic gate resistance of a mosfet is usually a few Ohms up to a few tens of Ohms.

ogden:

--- Quote from: treez on October 06, 2018, 03:29:01 pm ---Thanks, but the intrinsic gate resistance of a mosfet is usually a few Ohms up to a few tens of Ohms.

--- End quote ---

Did you read document? It has all info you need.

I may stand corrected, but I would calculate Rgs_internal this way: First calculate (initial) current of Td_on and Qgs mesurement, Igs = Qgs/Td_on. Then Rg_internal = Vgs/Igs - Rgs_external. As we know that Vgs used is 10V, calculation is: Rgs_internal = (10 / (Qgs/Td_on)) - 25. Thing is that Td_on specified is quite a range, 50..110 ns, so you shall calculate for min/max

[edit] Approach above is not correct. Better just use RG_internal from datasheet or assume it being around 1 ... 1.5 Ohms or so.

T3sl4co1l:
Their 25 ohm test is going to be too slow to derive an accurate R_G figure from.

Tim

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