plot gm/gds vs gm/id

[fat_123]

hello,


i am doing gm/id technique and for that i have to plot intrinsic gain i.e gm/gds

since in MOSFET we can directly plot it.

But i am doing it for CNFET so could anyone help me out and tell me how to plot gm/gds in other devices?

 

[pancho_hideboo]

But i am doing it for CNFET

What do you mean by "CNFET" ?

Show me followings.

(1) Simulator Name
(2) Post Processing Tool Name

 

[fat_123]

okay so CNFET means carbon nanotube field effect transistor.

i am doing it on HSPICE

 

[fat_123]

Show me followings.

i was asked to plot gm(by sweeping vgs and vds=vdd/2) and in another file plot gds(sweeping vds and vg=vdd/2)
and them combine them.but it gave a straight line.

please suggest me something i am stuck here.

 

[pancho_hideboo]

CNFET means carbon nanotube field effect transistor.

How do you implement CNFET in HSPICE ?
What device model do you apply as CNFET in HSPICE ?

i was asked to plot gm(by sweeping vgs and vds=vdd/2)
and in another file plot gds(sweeping vds and vg=vdd/2)

How do you evaluate gm and gds ?
What analysis do you use ?

I don’t think .OP is valid for CNFET.

What post processing tool do you use for HSPICE ?
AvanWave ?
CosmosScope ?
Custom Waveviewer ?

 

[fat_123]

CNFET model i took from stanford

i plotted gm by sweeping vgs and set vd=vdd/2 and got the gm(right) curve

i did the dc analysis

but i am stuck for plotting gds

yes .op is not valid

 

[fat_123]

i am using custom waveviewer

 

[pancho_hideboo]

CNFET model i took from stanford

Can you understand device model in HSPICE surely ?

What model do you use ?
Macro Model based on some FET model which HSPICE has natively ?
Compact Model based on Verilog-A description ?

i plotted gm by sweeping vgs and set vd=vdd/2 and got the gm(right) curve
i did the dc analysis
but i am stuck for plotting gds

Can you understand gm and gds surely ?

You have to evaluate derivative of Id regarding Vgs and Vds, if you rely on DC analysis.

Do you evaluate derivative of Id surely ?
Derivation is a function of Custom waveviewer not HSPICE.

 

[fat_123]

Stanford CNFET Model - HSPICE taken from Stanford site

32nm technology model.



yes gm=dId/dVgs gds=dId/dVds
i did the derivative of id w.r.t vgs and attached the gm plot

but how to do the same for gds and plot intrinsic gain

 

[pancho_hideboo]

Stanford CNFET Model - HSPICE taken from Stanford site
32nm technology model.

You can not understand device model for simulator at all.
32nm technology model has no relation at all.

Learn device model and simulator surely.

If you use Stanford University VS-CNFET(Virtual Source CNFET) Model,
it is a Compact Model based on Verilog-A description.

You can extract gm and gds as internal calculation result, if you can understand model equations.

but how to do the same for gds and plot intrinsic gain

Surely learn and understand Custom Waveviewer.
Or use functions of ACE(Analysis Command Environment) manually in Custom Waveviewer.
Actually your operation using GUI is done by function of ACE.

If you choose other post processing tool in stead of Custom Waveviewer, you can use MATLAB or Octave with HSPICE Tool Box.
https://www.cppsim.com/download_hspice_tools.html

 

[fat_123]

we cant just plot gds like gm.
i want to design opamp. for that i am doing gm/id technique and for single n-fet and p-fet plotting gm,gds,id/w

 

[pancho_hideboo]

Show me netlist for both gm and gds.
And show me sx log file of Custom Waveview.

 

[Puppet123]

these are instructions for cadence spectre

http://32mosfets.com/32mosfets/cadence-tutorials-2/cadence-tutorials/plot-gm-and-gmid/
**broken link removed**
http://www.ece.tamu.edu/~spalermo/ecen474/hw2_notes.pdf

 

[pancho_hideboo]

these are instructions for cadence
http://32mosfets.com/32mosfets/cadence-tutorials-2/cadence-tutorials/plot-gm-and-gmid/
**broken link removed**
http://www.ece.tamu.edu/~spalermo/ecen474/hw2_notes.pdf

First, model is a compact model based on Verilog-A, so operation point infomations of gm, gds, etc. are not available.

Second, he uses HSPICE and Custom Waveview.

 

[Puppet123]

The Stanford Model is here: https://nano.stanford.edu/stanford-cnfet-model

He can use Spectre with an HSPICE model, last time I checked.

 

[vivekroy]

I checked the source code for verilog-a implementation for carbon nanotube fets and I could not find the definition of gm.
But I know other veriloga models, for example for BSIM-IMG, the operating parameters are defined.