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Simulators >> RF Simulators >> Turn off thermal noise in SpectreRF simulation
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Message started by bluepisces on Jul 31^st, 2004, 9:23pm

Title: Turn off thermal noise in SpectreRF simulation
Post by bluepisces on Jul 31^st, 2004, 9:23pm

Hi,

For some reason, I have to model an ideal MOS without any noise. By setting kf=0 in BSIM3v3 model, flicker noise will be zero. However, I have no idea how to make a MOS thermally noiseless in SpectreRF simulation. Since many properties are affected by temperature, it would not be a good idea to reduce temperature. Thanks for any response.

???

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by August West on Aug 1^st, 2004, 1:29am

There is no direct way of doing this that I know of, though you might take a close look at the noise parameters ('spectre -h bsim3v3' if using bsim3). You might find a global thermal noise scaling factor that could be set to 0.

I've seen two basic approaches to getting around this problem, neither are very satisfying. In one, you basically build a duplicate MOS model in Verilog-A but without the noise sources and use it for the noiseless device. The other approach is to continue to allow the device to be noisy, but simply do your own computation of total output noise or whatever you are interested in, but exclude the individual contribution from the device that you would like to be noise free. The individual noise contributor summary gives you enough information to do this.

-August

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by Andrew Beckett on Aug 2^nd, 2004, 1:29am

One should ask why you want to have a noiseless transistor in
simulation? Do you have some magic process which allows the device to be noiseless in manufacturing ;-) ?

Andrew.

P.S. I don't know a way of making an individual transistor noiseless (resistors can be made noiseless, using the isnoisy=no option).

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by August West on Aug 2^nd, 2004, 6:08pm

I believe the parameter you need is gamma (at least for bsim3v3). I think if you set gamma to 0 the thermal noise of the channel goes away. If you also set kf to 0, the flicker noise goes away. You would have to set the value of any parasitic resistors to zero go get rid of their thermal noise.

-August

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by bluepisces on Aug 3^rd, 2004, 6:23am

Hi!

Yes! It works if I add "gamma=0" in the BSIM3v3 model and set all the parasitic resistances to zero.

Of course, I can't make the device noiseless in reality.
Why I do this is for the study of noise contribution from each device.

Thank you! :)

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by Eugene on Aug 4^th, 2004, 1:18pm

Doesn't the "print noise summary" list the noise contribution from each device so that you don't have to make individual devices noiseless?

Title: Re: Turn off thermal noise in SpectreRF simulation
Post by bluepisces on Aug 9^th, 2004, 8:56am

Hi, Eugene

What I want is the phase noise.
So, "print noise summary" doesn't fit my demand.
I don't know if SpectreRF can list "phase noise summary". If so, that would be great!