Model parameters

Did you consider reading the documentation? There's a whole manual on the device model equations, plus documentation on the parameters available for each mode. Run "cdnshelp" from <MMSIMinstDir>/tools/bin to get to the documentation.

If you want to plot the threshold voltage, the best thing to do is to create an include file, called (say) save.scs with the contents:

save M1:vth

and then reference this file from Setup->Model Libraries or Setup->Simulation Files. Then you can see this parameter from the Results browser after your dc sweep. Of course, change M1 to be whatever the device name is in your case.

Regards,

Andrew.

Hi Andrew,

I went through this thread and am interested in plot vth through DC sweep. But I received this warning：

   WARNING (SPECTRE-8282): `M1a' is not a device or subcircuit instance name.

    WARNING (SPECTRE-8287): Ignoring invalid item `M1a:vth' in save statement.

    WARNING (SPECTRE-8282): `M6' is not a device or subcircuit instance name.

    WARNING (SPECTRE-8287): Ignoring invalid item `M6:vth' in save statement.

I am sure the name is correct and is copied from schematic instance name field.  

 Do you know how to fix it?

Thanks,

 Alex

Presumably the name is not correct, or you've not given the correct hierarchical path to the instance. Look at the netlist itself - that's the best bet.

Regards,

Andrew.

Hi Andrew,

You can refer my snap cut. The naming is correct. I do not know how to check that hierarchical path. But the netlist is enough I think. 

 Regards,

Alex 

Alex,

The transistors you're trying to save the vth for are inside the _sub0 subckt, and you didn't tell it the hierarchical path to them. Since there is only one instance of that subckt, ie instance I0, you'd need:

save I0.M1a:vth

(assuming that the model pch is not a subckt itself).

Regards,

Andrew 

Hi Andrew,

 In my case I have seen that subckt _sub0.  But wher is the instance info? As you exampled, the instance I0, what is the only instance name in my design from previous snapshoot?

 Thanks,

Alex 

Alex,

All I did was read your netlist in your post. It's not difficult!

Andrew,

I have no warning now. I assume that I have saved vth of M6 by including "save I0.M6.vth". But this thread mentioned plot this variance by DC sweeping. How can I plot it with the help of result browser. You can point it out direct in this figure .

Thanks,

Alex 

Alex,

Firstly it would be "save I0.M6:vth" (note the colon) - check the spectre output as it will tell you if you have got it wrong.

Secondly, you're looking at the dcOp output there, not the dc sweep output. That's the (initial) DC operating point. You'd need to look in the "dc-dc" output in the results browser, and then you should be able to plot a waveform of I0.M6:vth versus the swept parameter.

Kind Regards,

Andrew.

Hi Andrew,

 Thank you so much. Now I have my desired plot.

Regards,

Alex.