How do I extract threshold of a device?

[dhaval4987]

Dear all,

I am using a technology and do not have information about its threshld and un.Cox parameters. I need to calculate the accurate Vth and Idsat for better design.

Suggestions, how do I extract those values?

 

[serhannn]

As far as I know, you cannot "extract" those values. At least, you need to know the zero subtrate-bias threshold voltage (VT0), source-to-body substrate-bias(VSB) and body-effect parameter (λ) to calculate the threshold voltage. Also, remember that the threshold voltage is temperature-dependent.

 

[sumansamui]

for a particular technology (0.09um,.18um...etc) those parameters are specific and you can find them from the library.

 

[birdy123]

Hi,
You can extract these information using .. EDA tools also.. these information uslly present in the foundry supplied data. The most important thing is here which tool are u using and which technology... so let me know .. these 2 .. I will try my best to help you.
One more thing .. please let us know which foundy data it is?

 

[thanhFF]

Perform a DC analysis on the component. Then check the result, you can see these parameters

 

[subhash_chevella]

hello,
Yes, YOU can extract the transistor parameter values usign the following procedure. I think it may help you.
I will tell you the procedure for NMOS transistor and you can apply the same to PMOS also.

First,
bias the transistor in Linear region.
Connect source to GND, Drain to 0.1V and vary the gate voltage from 0 to 3V.
Plot Id Vs Vgs (Drain current Vs Gate to Source voltage).

the current equation in linear region is
Id = UnCoxW/L(Vgs-Vth-Vds/2)Vds
this can be written as

Id = (UnCoxW/L*Vds)Vgs - UnCoxW/L(Vth+Vds/2)Vds

From the above plot you can find the max slope.
equate this slope value to UnCoxW/L*Vds. From this you can find UnCox value.

at that max slope point, extract the corresponding Id and Vgs values from the plot.
after extracting substitute these values in the above equation to find the intercept value.
equate this intercept value to UnCoxW/L*(Vth+Vds/2)Vds. From this you can find the Vth value also.

For some technology, example 180nm, fix L value to 180nm and change the W value and find the corresponding values of UnCox and Vth and make a table of those values. because as W changes UnCox and Vth also changes. you can observe these changes in the table.
From that table you can conclude one particluar value of UnCox and Vth of the transistor for this particular technolgy.

Due to temperature also these values may vary. this variation can be neglected for the design.
Using these values you can desing better circuits also (neglecting temperature effects).

You can find the Lambda, body effect parameter also. I didn't remember the procedure right now.
I will tell you that procedure once I verified that.

You can use Cadence or Spice tools for extracting these values.

regards,
Subhash