From looking online, a low R(DS) ON resistance at 3.3 volts appears to be ~ .013 Ohms. Somehow I keep messing up my current calculation and therefore my power loss calculation. I think it’s because I am calculating the current for the FET and not using the 26UA for the power loss calculation?

Power losses are found by the R(DS) ON of the device and current load:

If I have a 3.3v supply and the R(DS) ON is 13 mOhms

I=3.3/.013 ohms = 253.8A? Clearly this is wrong

Power loss = (I)^2 *(R)= (253.8)^2*(.013) = 837 Watts

There’s no way that current calculation is correct… Mostly I’m confused why this gives me the wrong answer.

I think this calculation is correct using the actual current the circuit will be using but I’m not sure. It’s much closer to what I’d expect, but I’m still confused why the previous current calculation doesn’t work:

Power loss = (I)^2 *(R)= (.000026 A) ^2*(.013 Ohms) = 8.7X10^-12 Watts

Should I also be taking into account the current the MOSFET consumes just to stay on? Thanks in advance