1. Cadence Tutorial
First: Annotate Results
To show the dc operating points of the transistors you are using in any circuit you could do the
following:
1- After you finalize your circuit and “check and save”, you must perform dc analysis, after that you
go to the results tab in the analog environment and select annotate then choose DC Operating
Points as shown in figure 1.
Figure 1
2. Then go to the schematic, you should see the following parameters next to your transistors: ids, vgs, vds,
vth and vdsat.
In order to see the regions or gds (1/ro), you should choose the edit tab in the schematic window, then
choose component display as shown in figure 2.
Figure 2
The window in figure 3 will open, make sure you select all things selected in figure3. Also you should
choose “select” the transistors you want to edit its component display from the schematic.
If you are using umc, you can find only 5 available places to show dc operating point, so you would have
to replace one to show other. Ex: if you want to show region, you must substitute vdsat or vds to be able
to add region.
If you are using tsmc, you will have 7 available spaces, so there is no problem just add region and gds.
Figure 3
4. Second: Sweep with gds (or any dc operating point)
For example we would like to sweep gds with the length of the transistor named “M1” as shown in
figure 5.
Figure 5
To do this, first go to the desktop and create a file “has extension .scs”, and add the line shown in figure
6.
To do this for more than one transistor, copy the line and paste but change the transistor name.
ex: save M1:all
save M2:all
save M3:all
Figure 6
5. After that go to the analog environment and open setup tab then choose simulation files as shown in
figure 7.
Figure 7
Then the window shown in figure 8 will be shown, so in stimulus files, add the path of the file we just
created “or browse it”.
You must make sure that in the dc analysis, you are sweeping with design variable or component
parameter. In our case we are sweeping with component parameter which is “L”.
After that you must Run the simulation.
Figure 8
6. After that go to tools tab in analog environment, and choose result browser as shown in figure 9.
Figure 9
The window open in figure 10 should appear, so choose dc-dc as shown in that figure.
Figure 10
The signals shown in figure 11 will appear, since we are only showing the dc operating points of one
transistor, we will find “M1/…” if you are showing more than one transistors, the list will be bigger and
you will find “M1/…” and “M2/…” , etc….
So for now we need to draw gds Vs. L, so double clock on “M1/gds”.
7. Figure 11
Finally a similar graph to that on figure 12 will appear. Remember “gds = 1/ro”
Figure 12
