Does a MOSFET need a gate resistor in the same way that a BJT needs a base resistor? If yes, what are the key datasheet parameters to consider in calculating the value for such a resistor?

Thanks in advance.

 

A gate resistor is recommended in most applications, but not for the same purpose as with a BJT.

A gate resistor limits the instantaneous current that is drawn when the FET is turned on. If you are driving a FET directly from a low-current device (microcontroller or logic gate) then gate resistors are recommended. Anywhere from 5 to 100 ohms is fine. They also can be viewed as slew-rate limiting devices for the gate signal, or as devices to eliminate ringing at the gate.

If you are driving the FET from something like a dedicated half bridge driver or similar then they can be eliminated, the drivers are usually meant to be directly connected to the FET.

 

I feel a gate terminator is also needed and many SMPS designs have it.
While in Microcontroller based designs the port pin responsible driving a mosfet gate would also discharge it when the pin is made LOW.

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Regards,
Sarma.

 

It's mainly just used to slow down how fast the MOSFET turns on and off in order to reduce ringing, voltage spikes, and interference (ie. if the gate driver can turn on the MOSFET faster than needed.)

 

As always - thanks.