So I’m trying to run a 3.7V motor off of a mosfet, and it works perfectly fine when I provide a 3.7V PWM signal to the gate of a FQP30N06L.
However, when I swap out that mosfet for the RFP30N06LE, it does not work. It did work when I provided it 9V however. I don’t understand why this is the case, I have compared the two data sheets and they are nearly identical, yet the LE does not seem to be even reaching its threshold voltage at 3.7V.
I have tried connecting the gate directly to a 3.7V rail instead of PWM pin but to no effect. I have 220 ohm resistors on the gate and I have tried with and without a 10k pulldown resistor, still nothing. Any ideas?
Best Answer
i agree with @Leroy105 on the fact that the fets may be different, however i wonder if you are connecting the source to the load rather than to 0v, that would rise the source voltage hence the gate source voltage would be lower which in turn may reduce the output current, and according to the datasheets of both fets that should happen in a more apparent in the RFP30N06LE since it has a slightly higher vTh which means that the voltage at the load should be lower for the fet to activate and hence lower would be the current at the load