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Gate resistors in MOSFET

Posted: 14 Dec 2017, 11:17
by jbc
Hi everyone,

what is the functionality of the 4,7ohm resistors in the gate of mosfets exactly?

Thank you
regards

Re: Gate resistors in MOSFET

Posted: 14 Dec 2017, 11:23
by ThierryGTLTS
1. To limit the driver current.

2. To improve switching and stability, less ringing.

So it's very important.

Have a Nice Day.

Thierry

Re: Gate resistors in MOSFET

Posted: 16 Dec 2017, 13:36
by pf26
When you want to control the MOSFET turn ON and OFF times, the gate resistor limit the gate currents and increase MOSFET switching times.
Otherwise, the dV/dt would be higher, would generate larger RF emissions, and could be destructive (because of components and pcb parasitic inductance and capacitances, playing unexpected role at higher frequencies).
So you need to find a compromise between higher efficiency (requiring low switching times) and safety (especially that turning ON the low side FET never makes the high side also turn on due to some coupling).

Re: Gate resistors in MOSFET

Posted: 15 Jan 2018, 13:00
by jbc
Now it is clear.

Thank you very much
regards