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threshold voltage question

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vhdl00

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i run hspice simulations recently, found that the threshold voltage is different for same device, i mean other than body effect, is there any other factors affect threshold voltage?
 

elec_student

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See threshold voltage is dependent on mainly four factors viz. Especially in submicron region :
1. Body effect
2. Built in potential
3. Charges introduced due to defects in fabrication

I don't exactly remember all four points.
U can refer Kang for CMOS. In 3rd chapter u will find this.
 

Fom

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Threshold also can be changed by DIBL effect if Vds voltages are different.
 

flamingo

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Maybe you use BSIM3 model for MOSFETs. There are about tens of paramenters effecting the vth, including mosfet's working condition, e.g., Vbs, Vds. You can refer to BSIM3 MOSFET model user's manual, good luck.
 

scottieman

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vhdl00 said:
i run hspice simulations recently, found that the threshold voltage is different for same device, i mean other than body effect, is there any other factors affect threshold voltage?
I guess you better clarify what's mean "the same device"

Same W, same L, same biasing condition ????

Otherwise, it is very difficult to comment on it

Scottie
 

firry

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vhdl00 said:
i run hspice simulations recently, found that the threshold voltage is different for same device, i mean other than body effect, is there any other factors affect threshold voltage?
if you give the same conditions on every terminals of your two same devices,you'll got the same threshold voltage in hspice,i believe.
 

Chethan

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apart from what elec_student wrote even temperature changes ur Vth
 

swathi0356

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WHT every body said on the above are absolutely correct.
but you can't say that two devices are same.
because even the beta values of two transistors is not same unless and untill we predict them as ideal.
sooo as it a mosfect you will not be able to get correct values of two vth of mosfects.
all the fators of mosfects come into pictures.
and sometimes will not be able to know some factors alsoo.
sooo, if you need same vth try to put everything same.soo tht for your hardwork atleast with point difference the vth of two mosfects will be equal ok
bye and all the best.
 

beckchm

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you can refer the different models.
 

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