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

## 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

# 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
• #### Fri, Nov 11 2011 1:58 AM

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