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region and reversed in transient results

syafiq
syafiq over 6 years ago

Hello,

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?

Thanks

Syafiq Mispan 

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  • Andrew Beckett
    Andrew Beckett over 6 years ago

    Hi Syafiq,

    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=n

    M1 (d g 0 0) nch w=1u l=0.2u
    M2 (0 g d 0) nch w=1u l=0.2u

    Vd (d 0) vsource dc=2
    Vg (g 0) vsource dc=1

    dc dc
    dcOpPoint 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.

    Regards,

    Andrew.

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  • syafiq
    syafiq over 6 years ago

    Hello Andrew,

    Thanks. Your explanation has clarified my concerns.

    Thanks

    Syafiq

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  • syafiq
    syafiq over 6 years ago

    Hello Andrew,

    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.

    Thanks

    Syafiq

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