open-source-silicon.dev

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I guess it is not the full testbench. Everything is shorted.

<@U03QSBWN0TU> The one on the left is a RF transistor. It has been characterized for high frequencies, but as such you are not allowed to change its dimensions or layout. If you look at the model you see W and L are fixed:
`+ lmin = 1.75e-07 lmax = 1.85E-07 wmin = 5.045E-06 wmax = 5.055e-6`

do you know why I get errors when I run it with the RF transistor?

(I didn't change anything and pressed simulate)

hmm if I delete the RF transitor it still fails

any idea how to fix the simulation and get it to run correctly?

<@U03QSBWN0TU> add command `remzerovec` before the write command:
```.control
save all
dc vd 0 1.8 0.01 vg 0 1.8 0.2
remzerovec
write test_rf.raw
.endc```


but it seems like the RF transistor has lower fT?

<@U03QSBWN0TU> The RF transistor should have specific values for Ad, As, Pd, Ps, ..., . If you just place the transistor and set W and L, xschem will use a simple formula to estimate these areas that contribute for parasitic effects. You should set these attributes to the actual value from the layout.
Anyway I don't know how reliable these RF models are.

how do I get the area and stuff? there's no documentation on the RF devices

<@U03QSBWN0TU>, if you have the original open_pdks cloned repository you can see the actual layout:

`..../open_pdks/sources/sky130-pdk/libraries/sky130_fd_pr/latest/cells/rf_nfet_01v8_lvt/sky130_fd_pr__rf_nfet_01v8_lvt_bM02W5p00L0p18.svg`
RF mosfets have double sided poly gate contacts to improve frequency response and dummy polys at the sides,  presumably to reduce drain/source parasitics.
However i don't know how to use these devices in the correct and accurate way. Don't know if you need to estimate Ad/As/Pd/Ps from the layout or just set these to 0. May be <@U016H5X1K62> can help you.