[SOLVED] Ft and Fmax

[ahmedatef0]

If I want to to find Ft & Fmax of the device can I use the nch model or should I use nmos rf.
In my opinion Ft and Fmax are in GHz so I should use the high frequency model (nmos rf) but wouldn't this
be simulating a model different than the one I'm going to use (nch)?

 

[BigBoss]

nmos_rf is a particular variant of nmos. Therefore you should use nmos_rf for RF applications.
The standard nmos device may also serve you up to certain point but it's not possible to say that the accuracy is definitely 100% correct.

 

[ahmedatef0]

nmos_rf is a particular variant of nmos. Therefore you should use nmos_rf for RF applications.
The standard nmos device may also serve you up to certain point but it's not possible to say that the accuracy is definitely 100% correct.

Yes but what if I want to characterize the device, clearly the layout of nmos rf would be different than nch so if I used nmos rf I wouldn't I be characterizing a different device?

 

[AMS012]

Both nch and nmos_rf will have different ft and fmax for sure. The major difference between the two are, 1) nmos_rf will have better modelling of parasitics for high frequency application (for GHz range), 2) nmos_rf will have substrate contacts also included (you can see the layout), and hence 3) the changes you see going from schematic sims to extracted or layout sims will be minimal.

You can choose the device that suits your requirement. BTW, you can also choose to customize the layout of either of these devices and make your own layout to improve ft and fmax. And my suggestion would be to always simulate the extracted layout model, as schematic sims are of no use anyway.