changing x-axis in spectre

[ee484]

Hi, everyone,

I am currently having trouble with setting some DC operating parameters as my x-aixs in Spectre.
Say, I do sweep DC with Vdc and it provide voltage supply to simple diode-connected NMOS.
Since I am sweeping with Vdc = Vgs, I can only plot a graph with a fixed x-axis, which is Vgs. Of course, I can use a calculator to change y-axis freely. However, I don't know how to change x-axis to other parameters other than Vgs in this case.

In Hspice. par() will do this job. But, I don't know how to do in Spectre.
Please help me out.

Thank you in advance!!
BJ

 

[skal81]

Let's say you sweep Vgs in the DC analisys and do a Vds sweep in a parametric analisys. If you plot the Ids you will have Vgs for the x-axis and several plot for the differents Vds.
Open the calculator, and with the "family" button select one of the curve. Then in the special function, choose "value" and enter the Vgs value u want (let's say 1V). The push plot.
You will have one curve with the Vds value on the x-axis and the Ids on the y-axis, corresponding to Vgs=1V.

I'm not sure it's what you want to do. If not can u give more detail so we can try find out the solution.

 

[ee484]

Thank you,
The techniques you suggested were very helpful.

Actually, what I wanted to do was the following.

I want to plot "gm/ID Vs. Vdsat".

However, I cannot sweep Vdsat. How can I make Vdsat be my x-axis?
(For example, since I am sweeping Vgs, Vdsat = VGS - Vth, thus if body effect is ignored, I just need to subtract Vth from Vgs sweep. But, how can I make Vdsat = VGS - Vth as my x-axis)
Basically, I want to know how to make any device paramter as my x-axis.


Thank you for your help!!!


BJ

 

[skal81]

Sorry for not answering before. Actually I haven't found the solution yet, that why.
But I got a new track. From the Calculator, open the browser. If you did a DC sweep, you will have in the tree:
psf -- dc-op --
in there you can find your transistor and the parameters, but I'm not sure how to plot yet.
Another track is the "OP" button. Select the transistor and you can choose to plot the internal parameters. But once again it's not the x-axis. I'll tell you if I found the way.
Sorry