Is it possible to disable the noises of some specific transistors when running pnoise

[iVenky]

Hi,

I am running pnoise for a VCO that I have designed for checking the phase noise. I would like to disable the some particular noise sources (like flicker, thermal etc) of some specific transistors to see the improvement in the phase noise after disabling. Do you know if there is a way to do it?

Thanks!

 

[SLK001]

No - absolutely not! These noises are from the physical environment of the semiconductor, ie, the bulk semiconductor. The best phase noise for a VCO comes from BJT and HJT transistors.

If you want better phase noise performance, start with a superior design.

 

[iVenky]

Actually I figured out one way. Under Simulations->Options->Analog, you can actually select the transistors whose noise sources have to be disabled. But then i am not able to choose a specific noise source like flicker or something like that. I can view the noise summary but I want to see the phase noise contribution

 

[erikl]

I would like to disable ... some particular noise sources (like flicker, thermal etc) of some specific transistors to see the improvement in the phase noise after disabling. Do you know if there is a way to do it?

Radio Eriwan ;-) : In principle yes - but it would be a tedious process: you'd have to exchange the model of that/these specific transistor(s) by a different model with exchanged (set to zero, or dismissed) just that/those particular noise source(s) and re-simulate (of course) - and repeat this back-change and new exchange for the next particular transistor(s) - OMG!

 

[SLK001]

You mean that you are looking for ways to remove the noise from a simulation? Why would you want to do that? Why would you want a simulation to be less accurate?

 

[FvM]

Radio Eriwan : In principle yes - but it would be a tedious process: you'd have to exchange the model of that/these specific transistor(s) by a different model with exchanged (set to zero, or dismissed) just that/those particular noise source(s) and re-simulate (of course) - and repeat this back-change and new exchange for the next particular transistor(s) - OMG!

Besides being meaningful, I wonder if it's possible for all noise sources. E.g. shot noise depends only on current and elementary charge, it can't be adjusted by any model parameter.

 

[crutschow]

You might try using an idealized VCCS (voltage controlled current source for a FET) or CCCS (current controlled current source for a BJT) in you simulations.
Those are perfect devices.

 

[pancho_hideboo]

Actually I figured out one way.
Under Simulations->Options->Analog, you can actually select the transistors whose noise sources have to be disabled.

Do you surely read my append ?
https://www.edaboard.com/threads/353014/#3

But then i am not able to choose a specific noise source like flicker or something like that.

You can make flicker noise disable by modifying device model file.
I always have two device model files with and without flicker noise.

I can view the noise summary but I want to see the phase noise contribution

I don't know what simulator you use at all.
There are many simulators which have analysis named as pss and pnoise.

Again do you surely read my append.
https://www.edaboard.com/threads/353014/#3

You can see noise contributions from various noise sources such as flicker noise, channel noise, shot noise, thermal noise, etc. in any vendor's RF type simulator.

The followings are Noise Source Names in Noise Summary Table of Cadence Spectre.

[MOSFET]
Drain Resistance Thermal Noise("rd")
Source Resistance Thermal Noise("rs")
Channel Conductance Thermal Noise("id")
Flicker Noise Source("fn")

[BJT]
Base Resistance Thermal Noise("rb")
Collector Resistance Thermal Noise("rc")
Emitter Resistance Thermal Noise("re")
Collector Shot Noise Source("ic")
Base Shot Noise Source("ib")
Flicker Noise Source("fn")
Burst Noise Source("bn")