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how to simulate noise in spectre

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chungming

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Hi~~
anyone know How to simulate noise in spectre?
If i have the spectrum of noise V/sqrt(Hz)
like attached file
How could calculate DC to 1KHz noise floor?
Is find it averagethen multiply sqrt(1K)?
thanks~~!!
 

chungming said:
Hi~~
anyone know How to simulate noise in spectre?
If i have the spectrum of noise V/sqrt(Hz)
like attached file
How could calculate DC to 1KHz noise floor?
Is find it averagethen multiply sqrt(1K)?
thanks~~!!
Click to expand...

In analog artist window, after you run the noise simulation,
Select, Tools -> Calculator.
Select the node where you want the noise voltage as AC option in the calculator.
Then, there is an integral function called integ(). Give the initial and final value as 0 and 1 kHz respectively. (If you give zero, sometimes the AC sweep will have problems if you run in log mode, so you can give 1 Hz). Then press the eval button. The output is the integrated noise voltage
 

thanks for your reply~~!!
but the result is so large .... is it correct~?
 

you can see spectre help on "pss" and "pnoise"
other, for little size device, the noise is big
 

chungming said:
thanks for your reply~~!!
but the result is so large .... is it correct~?
Click to expand...

The result may be large because at low frequencies - DC to 1 kHz, because you are mainly integrating flicker noise (for mos inversely propotional to area). Thermal noise contribution will be usually very small. So if you have small area devices, you flicker noise contribution will be large. The accuracy of this noise simulation depends on how well the flicker noise is modeled for the technology.
Also, get your noise in V²/Hz and then integrate it, rather than integrating V/sqrt(Hz), because the integration should give Hz, not sqrt(Hz) term.

Bharath
 

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    chungming

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