Monte Carlo - Virtuoso IC 6.1.5

First of all, I would suggest looking at your device models. If you look at the model files that are included in your netlist (i.e. those referenced from ADE) and check to see if there is a statistics block in the model files. This will look something like this:

statistics {
    process {   // process: generate random number once per MC run
        vary rshsp dist=gauss std=12 percent=yes
        vary rshpi dist=gauss std=rshpi_std // rshpi_std is a parameter
        vary xxx dist=lnorm std=12
        vary uuu dist=unif N=10 percent=yes
        truncate tr=2.0 // +/- 2 sigma
    }
    mismatch {  // mismatch: generate a random number per instance
        vary rshsp dist=gauss std=2     
        vary xisn dist=gauss std=0.5    
        vary xisp dist=gauss std=0.5    
        truncate tr=7.0 // +/- 7 sigma
    }
}

Probably just doing "grep statistics *.scs" would be a good start to find it. Check to see if there's a mismatch section.

Assuming all looks OK there, the models themselves need to be subckts. Mismatch is applied to each subckt and then the models within those subckts can be unique. If the transistors you are using are just direct models (without a subckt around them), then no mismatch will be applied. Some technologies have different components for mismatch than for normal use (for strange reasons).

Not sure if you said, but what technology are you using?

Regards,

Andrew.

First of all, I would suggest looking at your device models. If you look at the model files that are included in your netlist (i.e. those referenced from ADE) and check to see if there is a statistics block in the model files. This will look something like this:

statistics {
    process {   // process: generate random number once per MC run
        vary rshsp dist=gauss std=12 percent=yes
        vary rshpi dist=gauss std=rshpi_std // rshpi_std is a parameter
        vary xxx dist=lnorm std=12
        vary uuu dist=unif N=10 percent=yes
        truncate tr=2.0 // +/- 2 sigma
    }
    mismatch {  // mismatch: generate a random number per instance
        vary rshsp dist=gauss std=2     
        vary xisn dist=gauss std=0.5    
        vary xisp dist=gauss std=0.5    
        truncate tr=7.0 // +/- 7 sigma
    }
}

Probably just doing "grep statistics *.scs" would be a good start to find it. Check to see if there's a mismatch section.

Assuming all looks OK there, the models themselves need to be subckts. Mismatch is applied to each subckt and then the models within those subckts can be unique. If the transistors you are using are just direct models (without a subckt around them), then no mismatch will be applied. Some technologies have different components for mismatch than for normal use (for strange reasons).

Not sure if you said, but what technology are you using?

Regards,

Andrew.