The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> Circuit Simulators >> How to plot Op Param of FET with swept DC analysis
https://designers-guide.org/forum/YaBB.pl?num=1177432027

Message started by eng on Apr 24^th, 2007, 9:27am

Title: How to plot Op Param of FET with swept DC analysis
Post by eng on Apr 24^th, 2007, 9:27am

Hi,
I'm using a FET in triode and I'd like to plot its Rds vs. Vgs for different Ws. To do that;
I'm sweeping Vgs in DC analysis and changing Ws with parametric analysis tool. The output is the Rds with the expression of "(1/OP("/M1" "gds")
However this setup does not give me multiple Rds versus Vgs curves for different W sizes as expected.
My guess is; in order to plot the Rds, I should do a setting so that simulator saves the op point of the FET during DC sweep. I don't know how/where I can do that.

Could you please help me with that?

thanks
eng

Title: Re: How to plot Op Param of FET with swept DC anal
Post by Geoffrey_Coram on Apr 25^th, 2007, 3:41am

A cheesy work-around would be to place multiple devices, if you don't have too many W values you want to test.

Title: Re: How to plot Op Param of FET with swept DC anal
Post by topquark on Apr 26^th, 2007, 3:04am

Hi eng,

If you're familiar with MDL, you can do this conveniently with two nested foreach loops

Code:

alias measurement Rds_vs_Vgs{
...
run dc (...)
...

export real Rds=(1/(M5:gds))
// To get Rds of the device
}
foreach Vgs from swp(start=.., stop=.., step=..) {
foreach W from swp(start=.., stop=.., step=..) {
}
}
run Rds_vs_Vgs

Check out the forum posts on MDL for some idea on this.

Good Luck!

Gau