Home > Community > Forums > Custom IC Design > Plotting Gm vs Vgs for different values of Vbs

## Email

Recipients email * (separate multiple addresses with commas)

Message *

 Send yourself a copy

## Subscribe

Intro copy of the newsletter section here, some intro copy of the newsletter. Instruction of how to subscribe to this newsletter.

First Name *

Last Name *

Email *

Company / Institution *

 Send Yourself A Copy

# Plotting Gm vs Vgs for different values of Vbs

Last post Wed, Jun 11 2014 4:54 PM by wgtkan. 2 replies.
 Started by wgtkan 11 Jun 2014 11:33 AM. Topic has 2 replies and 1554 views
• #### Wed, Jun 11 2014 11:33 AM

• wgtkan
• Joined on Wed, Jan 30 2013
• Gainesvlle, FL
• Posts 54
• Points 870
Plotting Gm vs Vgs for different values of Vbs
 I would like to plot Gm vs. Vgs for different value of Vbs.Here is what I did. I performed DC sweep on Vgs and then plotted the drain current vs Vgs and then carried out derivative of ID with respect to VGS using the calculator, i.e derv(IS(drain)) to obtain GM. Then performed a parametric analysis of different values of Vbs.Then when I did hand calculation, the result doesn’t match.I read on this forum that first I have to do parametric analysis of Vgs and then go to ADE and tools > result browser >dc OPInfo then plot gm but it only plots one Gm vs Vgs not at different Vbs. What am I doing wrong?I have found a tedious method where I plot Gm vs Vgs for different values of Vbs by plotting them one by one meaning I plot Gm vs Vgs at one value of Vbs and then add it to the table, then I do the same for the next.My version is IC6.1.6-64b.500.2.1 Gm_Vgs.png
• Post Points: 20
• #### Wed, Jun 11 2014 2:41 PM

Re: Plotting Gm vs Vgs for different values of Vbs
 You could directly get the gm from the transistor, which doesn't get saved during a swept analysis (e.g. dc sweep or transient). So create an include file called (say) "save.scs" (make sure you have a .scs suffix) containing:save M1:gm(note that the M1 should be your transistor name). Include this via Setup->Model Libraries.Then do a dc sweep where you sweep Vbs. And a parametric analysis around that where you sweep Vgs. You can then go to the results browser, and for the dc analysis (not dcOpInfo) plot M1:gm.Andrew.
• Post Points: 20
• #### Wed, Jun 11 2014 4:54 PM

• wgtkan
• Joined on Wed, Jan 30 2013
• Gainesvlle, FL
• Posts 54
• Points 870
Re: Plotting Gm vs Vgs for different values of Vbs
 Dear Andrew:  I created an include file using a text editor in my case (gedit) and saved is as save.scs which contains save T1:gm the name of my transistor is T1.  I included this in ADE via Setup-> Model Libraries. First I did a dc sweep of Vgs from 0 to 1.5 in a linear step Mode of total 100 points. Then I did and a parametric analysis of values: Vbs1=-1, Vbs2=-0.75, Vbs3 = -0.5, Vbs4 = -0.25, and Vbs5 = 0. Then I went to ADE->Tools->Results browser->dc->T1/gm -> plot. I got it.   Thank you very much indeed.   GmvsVgs.png
• Post Points: 5