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Find Threshold voltage from Id-Vgs

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fat_123

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Hi,

Could anyone tell me how to find the threshold voltage from Id-Vgs characteristic in HSPICE?

Regards
 

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Vth is really an approximation. What will happen if in your plot you convert you vertical axis to a logarithmic scale?
 
It is basically for beyond CMOS technology.

Its logarithm plot looks like this.

vgs=sweep from 0 to vdd
vd=vdd/2
 

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The initial linear part of the curve is weak inversion, then a transition to moderate inversion adn finally strong inversion. So, if we believe the simplified theory that weak inversion is also sub-threshold region, then your threshold is somewhere at the meeting point of weak inversion and moderate inversion. But it is fuzzy.
 

For modeling purposes regress the sqrt(Id) vs Vgs curve
to its y-intercept. If you want to use a MOS model,
or just to talk to MOSFET people.
 

this is not a MOSFET, its an NCFET(negative capacitance feet) which works in subthreshold region.
 

Well, if you have a different model in mind then its
parameters ought to be documented and the equation
(or equations) that contain "VT" can be back-solved in
the same manner.
 

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