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Imagine that the left pulsor here is an arduino or a pi and now ignore it.
It is presenting an output of say 3.3V as the pulse source from the left, ready for the mosfet gate.
See how the 1kΩ resistor forms a divider with the 20kΩ . That middle point gives our voltage V to the mosfet gate.
The 20kΩ is our pull-down resistor which helps to pull that middle V to earth zero volts and so close the gate.
Keep the 1kΩ in place to protect the arduino/pi pin.
View the gate bar on the mosfet working fully and nicely, then look at the oscilloscope to explain the events:
Look at the y-axis vertical scale on the left.... the diagonal voltage moves from 0 to nearly 3.3v for the gate.
When it reaches 2V however, the gate opens and the load current flows instantly (seen in green) up to 3A
V=12 and R=4 as seen there for the load on the right, so we are getting the full green 3A flowing flat nicely.
When the near 3.3v pulse is turned off, the diagonal volts line drops back to zero, shutting the gate at 2V.
The 2V cut off/on point here where gate closes/opens and the green current stops/starts flowing is called the 'Gate Voltage Threshold' point. Vgs₍ₜₕ₎
You can set that in EC to conform to your bought mosfet as per its datasheet mentioned point.
In the EC settings it is called VTO..it is not always set at 2V, Try changing it to 1.5V in the mosfet settings here.
The 4Ω resistor here represents a load such as LEDs etc, but if there was an inductive load such as a motor, then the current flow would be a little different...close the switch to simulate a variation of that here if you wish.
Either way, notice how the green current rapidly shoots up to its maximum value. That all normally happens within the first volt after the Vgs₍ₜₕ₎ ie: from 2v to 3v here. The amount of current allowed in that 1v change is called the Transconductance, seen as S on the datasheet of a mosfet. You can alter the amount of current flow in that 1v change in EC by using the KP setting in the mosfet. Doing that will often get the gate to open and close fully, like a real mosfet would....a half open gate usually means that the mosfet switch is not set properly, and there is a waste of power with heat at the mosfet..... Try altering the KP in the mosfet setting here...turn it fully anti-clockwise and so prevent enough current from flowing in the pulse time...see how the green line takes too long....the gate is switched off before the max current is reached...now turn it clockwise until full current is obtained within the first 1v after the cutoff point....that is what you should normally aim for, giving a lower V across your mosfet whilst it is switched on.
(Give the old lines time to fade out to see results).
There are more aspects to a mosfet, but hopefully this has been some help with mosfet threshold and transconductance, and how to set those in an EC mosfet.
See here http://everycircuit.com/circuit/5927322113015808
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