I was looking at the transient results (using result browser), I saw two parameters which are region and reversed.
I belief region is referring to operating region of the MOS transistor as below. But I need a confirmation from you guys if this is correct?
region = 0 : cut off
region = 1 : linear
region = 2 : saturation
region = 3 : sub-threshold
region = 4 : breakdown
Another thing which I completely unsure is reversed. What does it mean actually by this parameter? It got number assigned into it.
example: reversed = 0. Could you help to explain what is 'reversed' and what the meaning of the number?
As far as I know, reversed is an indication that the transistor is connected the opposite way to the convention - in other words for an NMOS device, the source voltage is above the drain voltage. So in this netlist:
// example showing two transistors, one "reversed"model nch bsim4 type=nM1 (d g 0 0) nch w=1u l=0.2uM2 (0 g d 0) nch w=1u l=0.2uVd (d 0) vsource dc=2Vg (g 0) vsource dc=1dc dcdcOpPoint info what=oppoint where=screen
M2 shows reversed=yes, and M1 shows reversed=no.
The region information can be seen by doing "spectre -h bsim4" (or whichever device you are using). In the Operating Point Parameters section it has:
1 region=triode Estimated operating region. Spectre outputs the number (0-4) in a rawfile. Possible values are off, triode, sat, subth, and breakdown.2 reversed Reverse mode indicator. Possible values are no and yes.3 ids (A) Resistive drain-to-source current.
The numbers are in the order listed.
For a "bjt" device, it shows:
3 region=fwd Estimated operating region. Spectre outputs number (0-4) in a rawfile. Possible values are off, fwd, rev, sat, and breakdown.
so the meaning is different dependent upon the device, as I stated above.
Thanks. Your explanation has clarified my concerns.
I got one more concern. I ran dc simulation to know my circuits operating region. Basically you can load the raw file into result browser and go to dcOpInfo to check the region of transistor. But I got quite a lot of transistor =256 transistors. My I know how to extract the region for every single transistor?
And another question what is the difference between Id and Ids? I thought both are the same which is referring to the drain current of the MOS transistor, but sometime it gave same value, sometime NOT.