justDIY
Active Member
Is it possible to use the on resistance of a mosfet as a current sensing resistor?
I'm interested in monitoring the current demands of a load, most likely under 5 amps, and rather than buy an expensive milliohm resistor, or wire a bunch of regular resistors in parallel, I thought about using the on resistance of a mosfet?
the irf3708 has an RdsON of 8 milliohms at 10v, but they don't show a graph of what it would be at 12v. The difference between 4.5 and 10 is only 1.5 mOhm, so the difference between 10 and 12 is probably too small to worry about?
anyway, here's my idea in diagram form:
I'm interested in monitoring the current demands of a load, most likely under 5 amps, and rather than buy an expensive milliohm resistor, or wire a bunch of regular resistors in parallel, I thought about using the on resistance of a mosfet?
the irf3708 has an RdsON of 8 milliohms at 10v, but they don't show a graph of what it would be at 12v. The difference between 4.5 and 10 is only 1.5 mOhm, so the difference between 10 and 12 is probably too small to worry about?
anyway, here's my idea in diagram form: