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Why is Vds(on) stated in FET datasheet?

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treez

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Why does page 2 of the 2N7002 FET datasheet give values for vds(on)?
No other fet datasheet does this.
It is confusing.
Surely, all they need to do is give Rds(on), and then the user can calculate vds(on) using Ohm's Law?

Are they suggesting that Vds(on) does not always equal Rds(on) * Id ?

Does the 2N7002 have some residual Vds(on)...such that if Id = say just 100uA, then vds(on) could be 0.1V? (rather like the saturation voltage of a BJT)

2N7002 NFET DATASHEET:
https://www.fairchildsemi.com/ds/2N/2N7000.pdf
 

Sorry if I am wrong, I believe that the specified Vds(on) value is the maximum value of the voltage that can be dropped across the FET when Id is maximum.
 
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yes, though I don't know why they state it.
Vds(on) = Id * Rds(on)
This is Ohm's law, so why do datasheets think people need to be reminded of ohm's law?
If the Id was just 100uA....would the Vds be Rds(on) * 100uA?

..WOOPS, ok sorry, just seen the graphs on page 4.....problem solved.......(I originally thought that maybe these little fets had a kind if residual vdson, like a Vce(sat) ,which they displayed even if Id was very low, obviously this is not the case)
 
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