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How to plot transit frequency in virtuoso

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tarjina

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Hi!
Can someone help me with "how to" of current gain versus frequency for small signal analysis?
I have looked into the following article:
https://community.cadence.com/cadence_blogs_8/b/rf/archive/2008/07/16/measuring-transistor-ft

I tried to run that for a NFET in Virtuoso with ADE (L) and Spectre simulator. But couldn't succeed.
But Virtuoso throws an error. As follows:

ERROR (ADE-1057): Could not evaluate expression
Name:'E1'
Expression:'dB20((OPT("/N0" "id") / OPT("/N0" "ig")))'
because of the following error(s)
("quotient" 0 t nil ("*Error* quotient: can't handle (nil / nil)"))
Ensure that the definition of the expression is correct.
​

Following are design params:

Vg (DC) = 600m V
Vd = 800m V
Vsin = Amplitude: 5 mV, freq = 10kHz, DC voltage=0, AC magnitude=0
The testbench is attached.

tb_ft_nmos1.jpeg

Can anyone help me out?
Thanks in advance.
 

You have to make an AC analysis, while your expression base on the transient operating points. Measure correct current like in the example from cadence community.
 

It says about all the s-parameters and h-parameters. Do I have to do that?
And how can I find AC operating points.

calculator.jpeg

Can you tell me which one would give the AC operating points?

TIA!
 

Hi,

all of the model parameters for any transistors are simulated and stored.
There is a method for extracting the parameters in virtuoso w/ spectre.

Maybe check this link:
https://www.designers-guide.org/Forum/Attachments/Gm_BY_ID_Methodology.pdf

I remember doing this with a dc sweep simulation and then going to Results Browser and
reviewing the different parameters (ft, intrinsic gain, gm, etc) for a particular transistor,
but I don't really remember the exact way how I did it.

Cheers
 

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