SPEAKER 1: Well, when V GS greater than VT, I'm going to
get a short circuit between the drain
and the source terminals.
And when I have a short circuit, then V DS is always
going to be 0.
And the current i DS is going to be determined by the
external circuit that is connected to the MOSFET.
So other circuit parameters will determine the current,
but the DNS terminals can take any current.
It's a short circuit.
But V DS is always going to be 0, and it
can take any current.
So let's do a very quick demo and take a very quick look at
what this looks like in real life using a scope.
And again, remember, this is a very
simple view of the MOSFET.
I'm making a lot of simplified assumptions in treating it
like a switch.
And I just want to caution you again that the actual MOSFET
behavior is quite a bit more complex.
And the switch calculation is a gross simplification.
If we're able to deal with the simple abstraction of a
MOSFET, then continue.
But if you really, really, really want to check out what
the details of a MOSFET look like and what it really,
really behaves like, then I would recommend that you go
check out section 7.3 of the textbook.
OK, so let's go to the demo and show you how the MOSFET
really behaved like a switch where it is short circuited
for one value of V GS and open circuited for a different
value of V GS.