Gate to source resistance

[Nimish]

How to determine the gate to source resistance for mosfets like irf840 and irfp460.


Is their any reason to put MOV across this resistances

 

[Tahmid]

Hi,
Usually a gate to source resistance is provided to prevent accidental turn-on due to noise or other factors or gate-to-drain internal capacitance (Miller capacitance). Normally I use 1k and it always works fine.
There is no need to put MOV across the resistance. Instead place a zener diode for providing gate-to-source protection from voltage spikes beyond the tolerable Vgs voltage.
Hope this helped.
Tahmid.

 

[Nimish]

i am using driver IC to fire mosfet.Is it necessary to use back to back zener diodes from gate to source.

 

[Tahmid]

Which driver IC are you using?
Back to back zener diodes aren't necessary, but provide at least one zener and resistor for protection.
I usually use a 1k gate to source resistance and a 15v gate to source resistor.
Hope this helped.
Tahmid.

 

[Nimish]

I am using ir2104 driver IC .

 

[Tahmid]

Hi,
Just use a 1k resistor from gate-to-source. You don't really require the zener since you're using a dedicated MOSFET driver.

 

[Mr.Cool]

i use bi-directional TVS instead of a zener for protection because it is just as likely to get positive spikes as it is to get negative spikes.

it is small price to pay for increased reliability.

Mr.Cool

 

[gutisie]

Hi, I am looking for someone who can explain how to calculate the following resistors in the picture below, taking into account the following.
N CHANNETL MOSFET IRFZ44N
P CHANNEL MOSFET IRF9510
batery lipo 2000mA 20c 11.1v
motor could pull upto 30A.
**broken link removed**

Thanks in advance.
Best regards.