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Design >> RF Design >> is it possible to turn off the noise sources?
https://designers-guide.org/forum/YaBB.pl?num=1165278936

Message started by Aigneryu on Dec 4^th, 2006, 4:35pm

Title: is it possible to turn off the noise sources?
Post by Aigneryu on Dec 4^th, 2006, 4:35pm

Just like the function I can use for a resistor.
Since there are so many noise sources in a transistor, is it possible to turn off a specific noise sources in a specific instance in noise simulation (pnoise)?

Title: Re: is it possible to turn off the noise sources?
Post by loose-electron on Dec 5^th, 2006, 2:26pm

Well, the reason they set things up to get noise free resistors is so that you can look at the noise contributors from just your circuit elements.

Since you have to live with this stuff in your design in the real world, why would you want to do this in a design?

puzzled in southern california,
:-/

Jerry

Title: Re: is it possible to turn off the noise sources?
Post by sheldon on Dec 6^th, 2006, 4:52am

If the intent of turning off noise sources it to understand which
noise sources are important, that is, contribute to the total noise,
then use the noise summary. The noise summary can be used to
analyze the results both small-signal and periodic noise analysis
(if you have access to ADE).

Best Regards,

Sheldon

Title: Re: is it possible to turn off the noise sources?
Post by Aigneryu on Dec 6^th, 2006, 9:54am

Yes, I know I can use noise summary but sometimes I feel it would be more convenient to directly plot the noise, especially when I want to check the cyclostationarity of each noise sources. For example, it would be very convenient to do so if I want to find the ISF function for each contributer in an oscillator.

Title: Re: is it possible to turn off the noise sources?
Post by sheldon on Dec 6^th, 2006, 9:02pm

Aigneryu,

Then just plot the noise contributions using the results browser. While
the ISF is not available, the PPV is available in the most recent release.

Best Regards,

Sheldon

Title: Re: is it possible to turn off the noise sources?
Post by Aigneryu on Dec 7^th, 2006, 7:36am

Thanks Sheldon,

Actually that's is exactly what I do currently. but I just want to find out an easy way to get the ISF function in order to
check if my derivation is correct or not since I am developing an analytical solution for oscillators. Rather than inject a
finite width pulse to the osc and measure the phase shift, which is practically difficult to estimate the measurement error,
I try to inject a white noise current to the osc and do the time domain pnoise. This should be much faster and more accurate
than transient approach since the circuit is linearized through PSS solution.

Sincerely,

Title: Re: is it possible to turn off the noise sources?
Post by loose-electron on Dec 7^th, 2006, 3:04pm

You can go into the transistor models and set the noise coefficients to zero, but it is messy to do.

Email Ken, he may know a way in Spectre...

Title: Re: is it possible to turn off the noise sources?
Post by Ken Kundert on Dec 8^th, 2006, 12:31am

I know of no way of doing it. I see no point to it. Turning off all the noise sources and then sequentially turning them on one at a time is hard and slow. You get the same information in the noise summary, and you get it from every noise source with one noise analysis.

-Ken

Title: Re: is it possible to turn off the noise sources?
Post by Aigneryu on Dec 8^th, 2006, 12:54am

Thanks, Ken,

You are right. why I asked for this is because when I browse the result for time domain noise,
not like in the direct plot menu, rather than plotting with the sweeping time index, it will give me many points
on the same frequency. But now I found there is an option to change the sweeping variable.