Internal Gate Resistance of MOSFET-Calculation

Thread Starter

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.


Thanks in Advance!

Regards,
B.Janani
 

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. :confused:
 

Thread Starter

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. :confused:
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.
 

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.


Thanks in Advance!

Regards,
B.Janani
Very few people have test instruments capable of measuring gate oxide leakage or resistance.

The principle cause of MOSFET losses are the voltage developed across RDSon at high drain current and the apparent "linear region" during switching transitions, which increase with switching frequency.

Gate leakage is insignificant with a DC potential - gate capacitance is somewhere in the general direction of 2nF, capacitive reactance comes down as frequency increases.
 
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