How can I get the small-signal output resistance by spectre?

[Question]

spectre transistor output resistance

How can I get output resistance of a transistor (ro) by spectre simulator in Cadence software.

I can only get the parameter ron from DC operating point. It is rds=Vds/Id, not ro=σVds/σId.

And I can get the λ from model parameter. Is it named pclm? But result of the formula ro=1/(λId) is not correct too.

Who can help me to get the small-signal output resistance?

Thanks!!

 

[Fom]

Re: How can I get the small-signal output resistance by spec

If you want to find derivative dVs/dIs, you can use calculator function "deriv" and calculate deriv(Vs)/deriv(Is). That means (dVs/dX)/(dIs/dX), where X is a DC sweeping variable and it will be equal dVs/dIs.
Good luck.

 

[jliang]

Re: How can I get the small-signal output resistance by spec

I think you can run a dc bias simulation, then results->print->model parameters. It will show gds, which is 1/rds.
Note: this is done using spectre

 

[Question]

Re: How can I get the small-signal output resistance by spec

I think you can run a dc bias simulation, then results->print->model parameters. It will show gds, which is 1/rds.
Note: this is done using spectre

what is the name of gds in model parameters? I cna not find this parameter.

Thanks!!

 

[sreechoudhary]

can any one post exact circuit and the results for DC-operationg point

Added after 14 minutes:

how to calculate dc,ac,trans responses of simple transistor in cadence spectre

can any one p[post with circuit

thanks in advance

 

[jliang]

Re: How can I get the small-signal output resistance by spec

oops, my mistake, it should be results->print->dc operation points.
It will show all the ss parameters.

Added after 2 minutes:

Forget to mention, after you select the command, you need to select the transistor you want in the schematic.