question: headroom and overdrive values in Cadence

[cmos_ajay]

Hello,
I am using Cadence for cmos analog ic design. I would like to see the headroom (vds - vdsat) and overdrive (vgs - vth ) for each MOSFET in my schematic. I know the Annotate -> Transient operating points tool in Cadence which displays vgs, vth, vds and vdsat individually beside each mosfet.

Since I am running this simulation over various process corners and temperatures, there will be several values of headroom and overdrive.
I would like to have a table generated with all those values.

How do I do this in Cadence ??

Thanks and regards.

 

[jimito13]

You can use the top menu of the ADE L environment with the following steps : Results --> Print --> DC Operating Points , then hit a left click on the transistor you want and hit escape.You will be prompted with a small table with all useful values for calculating the ovedrive voltage and the saturation voltage (Vdsat).

I guess for a more summarized table will just some of the desired parameters and not all of them listed after the steps i suggested you above,you should turn to some SKILL code...i am not expert at all with this,so expect from somebody else to give an answer for this.

Regards,
Jimito13

 

[erikl]

In addition to jimito13's suggestion, you could use ADE's calculator to take care of the headroom (vds - vdsat) and overdrive (vgs - vth ) calculations. Then save your session to an OCEAN (.ocn) script, so you can edit and rerun it.

BTW: The "region" number backAnnotated to the schematic also differentiates between linear (vds - vdsat < 0) and saturation (vds - vdsat > 0). For more info about the region numbers, s. this thread. The region numbers are explained at the end of this thread.

 

[checkmate]

I did it by referring to the "Component Description Format User Guide" under Appendix B (Accessing Schematic Primitive Model and Operating Point). You have to customize towards your simulator. Also, my implementation caused oppoint displays to be corrupted after some time, so no guarantees that it actually works.