# open drain terminal of an nmos

if drain terminal of an nmos is open and source terminal is connected to 1v+ and the gate is also biased to a positive voltage, the Id=0 and Vds=0. can anyone explain? especially "Vds=0" I thought when a terminal is open it means we don't know its voltage, how does it say: Vds=0??

• The terminal is not externally connected, but there is a small amount of leakage (nA, probably) inside the MOSFET to the terminals that are connected that will cause the drain terminal to be at the same potential as the source and gate. If the whole MOSFET was floating you would be correct, at least in theory. Imagine a large value resistor, say 10G$\Omega$ always internally connected between drain and source. Oct 10, 2016 at 7:15