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Is the above schematic Mosfet in Ohmic or is it in Saturation?
It is in Saturation.
We know that because the little gate bar is not fully showing !
Now go to the bottom left gate supply (called Vg), and gently turn up that gate volts from its present 8.65v to 8.66v .... see how the Mosfet gate bar now shows fully:
When the gate bar shows full, the Mosfet is in the Ohmic region ready for switching adjustments.
When the gate bar is half shut, the Mosfet is in the Saturation region ready for amplifier adjustments.
When there is no gate bar shown, the Mosfet is OFF, virtually no current will flow down the drain (Id=0)
From now on, whenever you set a Mosfet in EC, you can see instantly by that gate bar whether the Mosfet is in the appropriate region for your task (full bar shown when on, if full switching is required).....
But your Nmos will need to be set to work properly for you .... e.g. keep lambda=0 and set others as reqd.
Now put the Nmos back to saturation, exactly as in my default schematic here.
Then turn the 10v top drain supply volts (called Vdd) up as much as you wish ....
e.g.... turn up Vdd to 20v and see the current (Id) through the drain resistor (called Rd).
Now turn that Vdd up to 10kV ....the Id through Rd stays exactly the same !
That fixed Id current through Rd is very useful to set a d.c. Q point for amplifiers, e.g. by using bias divider resistors, but we don't want to keep a fixed low unknown current when turning on a full switch.... We don't want the Nmos in amplifier saturation mode there. We want the Vd to drop fast with the Id rising fast till the max. Id is available as set by the Rd here.... with no restriction imposed by the Nmos.
Now turn everything back to its default schematic here again.
Then put the Mosfet in to the Ohmic region by turning up the bottom left gate volts to 20v ie Vg=20V
See the full gate bar, showing you that the Nmos is in the Ohmic region.
Now turn up the top Vdd a little at a time .... see how the drain current Id, through Rd now alters... not holding fixed as it did when the Nmos was in Saturation. (until the max. Id is reached, determined by Rd, not Nmos).
Ohmic for full switching....the Id will alter.... full bar shown.
Saturation for amplification.....the Id will hold fixed even if Vdd is altered.... half bar shown.
....keep an eye on the bar.
Notice that as you turn up Vg, the drain voltage (called Vd) drops.
If you increase Vg too much, then the Vd will drop down to a level which turns the Nmos from its Saturation in to the Ohmic region. (The little gate bar will fully open when the Mosfet flicks in to the Ohmic region).
Turning up the Vg will turn up the Id and it will lower the Vd
Play with alterations, and see how the Vd needs to be watched to prevent it from dropping down enough to flick the Nmos in to Ohmic, thus altering what happens to Id in the two different regions ....
You now have the ability to select your region and change it or hold it...ready for further alterations as required for either switching or amplification circuits.
Next .... More usable detail for all of that, not just watching the gate bar.
Page 3 here: http://everycircuit.com/circuit/6179495276183552
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