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CMOS Current in triode region equation

  • Thread starter Dhruv
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Homework Statement


Q. I was given a equation for PMOS and NMOS drain current in triode region but I am having some confusion regarding equation please do help.

I think drain to source current in PMOS should be negative but in equation value will come out to be positive if I keep V(gs)
,V(ds) as negative .

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  • #2
rude man
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I wouldn't waste too much time worrying about mathematical polarities.

You know that an NMOS requires the gate to be more positive than the source by at least the threshold voltage Vth, and the drain more positive than the source, and you know the current runs from drain to source.

Similarly, you know that the gate of a PMOS has to be more negative than the source by Vth, and the drain more negative than the source, and that the current runs from source to drain.

That's all you need to know. Spec sheets can be obfuscative if you lend too much credulity to signs.
 

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