# Internal Gate Resistance of MOSFET-Calculation

#### Janani_Rajkiran

Joined Nov 1, 2016
46
Hi

Is there a method or formula to calculate the Internal Gate resistance of a MOSFET

This information is missing in some of the MOSFET Datasheets and it is hard to calculate the MOSFET Switching losses without this particular information.

I do not want practical methods to test the MOSFET and find the Internal gate resistance.

There are already many articles on it.

This is for a preliminary assesment.

Regards,
B.Janani

#### kubeek

Joined Sep 20, 2005
5,724
I guess you could measure it the same way you measure ESR of a capacitor.

#### crutschow

Joined Mar 14, 2008
24,952
The MOSFET gate resistance has no effect on the gate switching losses.
This is determined by the energy to charge and discharge the gate capacitance (FCV²).

The other switching loss is determined by the switching speed as it goes through the linear region, and that speed is given in the data sheet.

Don't understand why you think you need the gate resistance. #### Janani_Rajkiran

Joined Nov 1, 2016
46
The MOSFET gate resistance has no effect on the gate switching losses.
This is determined by the energy to charge and discharge the gate capacitance (FCV²).

The other switching loss is determined by the switching speed as it goes through the linear region, and that speed is given in the data sheet.

Don't understand why you think you need the gate resistance. Hi,

Please check the attached application note Page 2 and Page 6

The Series gate resistance is important to calculate the switching Loss of a MOSFET and also it affects the switching time.

This is why I need the parameter

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#### Alec_t

Joined Sep 17, 2013
11,277
If the datasheet doesn't specify Rg you could (in theory) measure it by determining the switching times when two or three known-value resistors are in turn connected in series with the gate, plotting a graph of time v added resistance and extrapolating to zero. I don't know how practical that would be though, given the small resistance values involved and inherent parasitics.

#### crutschow

Joined Mar 14, 2008
24,952
The Series gate resistance is important to calculate the switching Loss of a MOSFET and also it affects the switching time.
The effect is small and is included in the switching times given in the data sheet.
If you think it's absolutely needed, then you will most likely have to measure it.

• Janani_Rajkiran

#### ian field

Joined Oct 27, 2012
6,539
Hi

Is there a method or formula to calculate the Internal Gate resistance of a MOSFET

This information is missing in some of the MOSFET Datasheets and it is hard to calculate the MOSFET Switching losses without this particular information.

I do not want practical methods to test the MOSFET and find the Internal gate resistance.

There are already many articles on it.

This is for a preliminary assesment.

• 