I was reading this OK tutorial to refresh myself on how to make a MOSFET switch. They do a good job explaining theory but they dont' take it that one step further. You can find more information here.
I took a n-channel depletion MOSFET model from here Simon Bramble
and I made a SPICE model circuit around it.
I stepped the voltage on the gate - look at the V(1) voltage in grey - and it activates the MOSFET conducting channel via the field effect when the blue line V(3) (which is the drain node ) drops from 6 volts down to zero. This causes the current to flow through the drain to source and this turns on the load which is flowing through I(Vss).
Erratum: First version explained effect as transconductance, that's not accurate I've changed it to field effect. That's how rusty I am I mixed the phenomena.Transconductance is a generalization relating transfer function in this case of gate voltage to compared to source current / voltage but the phenomena is the field effect. My first explanation was partly correct but the second one is completely accurate.
I took a n-channel depletion MOSFET model from here Simon Bramble
and I made a SPICE model circuit around it.
I stepped the voltage on the gate - look at the V(1) voltage in grey - and it activates the MOSFET conducting channel via the field effect when the blue line V(3) (which is the drain node ) drops from 6 volts down to zero. This causes the current to flow through the drain to source and this turns on the load which is flowing through I(Vss).
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