Home > Community > Forums > Custom IC Design > Sensitivity analysis of subcircuit

Email

* Required Fields

Recipients email * (separate multiple addresses with commas)

Your name *

Your email *

Message *

Contact Us

* Required Fields
First Name *

Last Name *

Email *

Company / Institution *

Comments: *

 Sensitivity analysis of subcircuit 

Last post Fri, Nov 11 2011 5:49 AM by ChrisEAS. 2 replies.
Started by ChrisEAS 11 Nov 2011 01:58 AM. Topic has 2 replies and 1271 views
Page 1 of 1 (3 items)
Sort Posts:
  • Fri, Nov 11 2011 1:58 AM

    • ChrisEAS
    • Top 500 Contributor
    • Joined on Thu, Jul 7 2011
    • Dresden, Saxony
    • Posts 18
    • Points 270
    Sensitivity analysis of subcircuit Reply

    Is it possible to do a Spectre sens analysis for a subcircuit? For instance having ..

     subckt inv ( a b )
     M1 ( a b vdd vdd ) pmos l=0.1u w=0.1u
     M2 ( 0 b a 0 ) nmos l=0.1u w=0.1u
     ends

     X1 (a b) inv

    .. I'd like to get the sensitivity of the current I(X1:a) against the voltage of a. Using a line such as ..

     sens ( X1:a ) to ( a ) for (dcOp )

    .. gives the error message "`X1': Not a signal, device instance or a model."

     Is there a way to achieve that?

     Thanks, Chris

    • Post Points: 20
  • Fri, Nov 11 2011 5:43 AM

    Re: Sensitivity analysis of subcircuit Reply

    Chris,

    I don't think this is possible. For a start, the to part has to be a component or instance parameter - it cannot be a voltage. Secondly, the output variable can't be a subcircuit current.

    I did manage to do it this way though:

      //

     global 0 vdd
     model nmos bsim4 type=n
     model pmos bsim4 type=p

     subckt inv ( a b )
     prb (a aint) iprobe
     M1 ( aint b vdd vdd ) pmos l=0.1u w=0.1u
     M2 ( 0 b aint 0 ) nmos l=0.1u w=0.1u
     ends

     X1 (a b) inv

     v1 (a 0) vsource dc=0.5
     vdd (vdd 0) vsource dc=1

     dcOp dc
     opts options sensfile="sens.out"

     sens (X1.prb:1) to (v1:dc) for (dcOp)

    But this may not be exactly what you want...

    Andrew.

    • Post Points: 20
  • Fri, Nov 11 2011 5:49 AM

    • ChrisEAS
    • Top 500 Contributor
    • Joined on Thu, Jul 7 2011
    • Dresden, Saxony
    • Posts 18
    • Points 270
    Re: Sensitivity analysis of subcircuit Reply

     Thanks, Andrew. This comes pretty close to what I was trying to do. Actually, my workaround was exactly that (unless that I've put prb outside the subcircuit). So if there's no other way of doing it, I'll stick with that. Thanks.

    • Post Points: 5
Page 1 of 1 (3 items)
Sort Posts:
Started by ChrisEAS at 11 Nov 2011 01:58 AM. Topic has 2 replies.