Dear all,
I need to drive an IRF630 (power N-channel MOSFET) from Arduino. I know this MOSFET requires a VGS of 10V to fully turn on BUT for my application I can work with 5V (I've tested it) and the power loss incurred is very minimal (it is almost fully on at 5V and my currents do not exceed 1Amp). Anyway, my question is this: With reference to the attached figures, would you prefer option A or B to drive the gate from the digital output of the Arduino ? Rser is there to limit any transient current and hence protect the digital port and Rpull is there to tie the gate to ground to avoid damage or the MOSFET from switching on when the gate is open circuited (if ever). Anyway, speed is not an issue here so I can live with Rser. My argument is: In option A the gate voltage would be a little less than 5V (because of the potential divider formed by the two resistors). I though of option B to solve the problem (I know it is a minor one in practice). But I am curious: would option B serve the same purpose better ? Thanks in advance.

 

My take...

Rser seems unchanged @ 1K
Rpull is changed to the combination of Rser and Rpull or 101K

It doesn't seem to matter to me, but wait till you get some other input.

 

Use option A, reduce Rser to 270 Ohms.

 

@ all: thanks for the replies. @ SgtWookie: isn't option B better ? In option A the resistors act as a divider and reduce the effective voltage at the gate from 5V to 4.95V. I know the difference is practically insignificant BUT I'm trying to save every mV of gate drive since I'm already using a low drive voltage for this MOSFET (usually a safe Vgs=10V). Anyway, the question is: isn't option B better ?

 

@ all: thanks for the replies. @ SgtWookie: isn't option B better ? In option A the resistors act as a divider and reduce the effective voltage at the gate from 5V to 4.95V. I know the difference is practically insignificant BUT I'm trying to save every mV of gate drive since I'm already using a low drive voltage for this MOSFET (usually a safe Vgs=10V). Anyway, the question is: isn't option B better ?

As Sgt. suggested, changing Rser to 270 ohms from 1K will give you a divider voltage of 4.999V

 

The idea is to turn off the MOSFET in case anything fails in the gate drive circuit.

Rpull will sink a negligible amount of current. It should be wired directly from the gate to source terminals.