I am using a P chan fet as a high side switch. The data sheet specifies a min Vgs threshold voltage (-0.45V @ 250uA) and a max leakage current (Ids<1uA @ Vgs=0); but does not provide a cut off voltage. Is there a rule of thumb or equation I can use to estimate the cut off voltage? Note: The "cut off" voltage is the value of Vgs "below" which the channel is shut off and only leakage current flows. I just need to determine the Vgs required to guarantee the Ids is below some very small number. It is not practical to get Vgs=0V; so how close to 0V does it need to be?
Maybe cutoff is the wrong term? How can I determine a safe Vgs such that the sub-threshold Ids is small enough, say < 1-2uA?
The question is really about mosfets in general but here is the data sheet link: NTJD4158C Datasheet