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surianova
Joined: 01 Sep 2004
Posts: 404
Helped: 21
Location: ASIA
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 10 Jan 2005 11:21 noise in transient |
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hi
Some question about noise, I get noise around 100nv/hz in AC analysis, but the problem is how can i apply this info in transient simulation? Thanks.
Suria
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terryssw
Joined: 18 Apr 2004
Posts: 176
Helped: 14
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| 10 Jan 2005 17:02 Re: noise in transient |
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| I don't think you can do it since the machanism of simulating noise and transient is different. You can only obtain the noise level by noise analysis, and keeping in mind that it is your noise floor.
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borodenkov
Joined: 02 Mar 2004
Posts: 129
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| 11 Jan 2005 3:26 noise in transient |
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| What you can do is to insert a nosie source with the PSD obtained from Noise simualtion to a behavioral (transient) model of your circuit and to estimate its effect on system performance. This technique can be used for example for PLLs or delta-sigma modulators.
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surianova
Joined: 01 Sep 2004
Posts: 404
Helped: 21
Location: ASIA
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| 11 Jan 2005 3:49 Re: noise in transient |
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| borodenkov wrote: |
| What you can do is to insert a nosie source with the PSD obtained from Noise simualtion to a behavioral (transient) model of your circuit and to estimate its effect on system performance. |
1.Any command for the noise sourse with the PSD?
2. how to do behavioral (transient) model ?
TX
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crazyamd
Joined: 11 Jan 2005
Posts: 41
Helped: 2
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| 11 Jan 2005 8:43 Re: noise in transient |
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| noise is measured by a PSD - often as the amount of noise in 1 Hz BW. To simulate in time domain, you need to simulate it for a fairly long period with very small steps so that the high freq noise is included. So ac or xf simulation is more useful.
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surianova
Joined: 01 Sep 2004
Posts: 404
Helped: 21
Location: ASIA
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| 11 Jan 2005 9:58 Re: noise in transient |
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| crazyamd wrote: |
| noise is measured by a PSD - often as the amount of noise in 1 Hz BW. To simulate in time domain, you need to simulate it for a fairly long period with very small steps so that the high freq noise is included. So ac or xf simulation is more useful. |
why run with long period with very small steps, high freq noise is included?
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terryssw
Joined: 18 Apr 2004
Posts: 176
Helped: 14
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| 11 Jan 2005 10:37 Re: noise in transient |
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| high-frequency components change value in very small time period, so if you want to simulate noise up to high-frequency, your time-step must be very small. This is also one of the reason why noise analysis do not embedded into the transient analysis in simulators since to cover all noise power with enough bandwidth, very small time-step must be used and this would very costly (and impossible) for transient simulations.
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surianova
Joined: 01 Sep 2004
Posts: 404
Helped: 21
Location: ASIA
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| 12 Jan 2005 3:17 Re: noise in transient |
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| terryssw wrote: |
| high-frequency components change value in very small time period, so if you want to simulate noise up to high-frequency, your time-step must be very small. This is also one of the reason why noise analysis do not embedded into the transient analysis in simulators since to cover all noise power with enough bandwidth, very small time-step must be used and this would very costly (and impossible) for transient simulations. |
But the noise i get is a low frequecy noise or what we call as fliker noise and it is not high frequency noise. How i can emulate the result i get in AC analysis in transient?
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layes2
Joined: 03 Dec 2004
Posts: 346
Helped: 5
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| 14 Jan 2005 10:48 Re: noise in transient |
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there is glitch in tran
just multipy the ac gain with the tran signal
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markty
Joined: 15 Dec 2004
Posts: 60
Helped: 2
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| 15 Jan 2005 2:28 noise in transient |
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| I think this can be done in behavior level simulation, matlab has such noise source. But in circuit level, i have no idea.
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borodenkov
Joined: 02 Mar 2004
Posts: 129
Helped: 11
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| 17 Jan 2005 1:45 noise in transient |
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Well, the main question here should be not HOW, but WHY! Why do you need to include noise in transient?
If you want to see, how device noise affects the work of your complex system (e.g. sigma-delta modulator or PLL) - build a behavioral model of your system (e.g. Matlab, Verilog-A etc) and include noise sources there with PSD obtained from noise simulation of circuit blocks.
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legend
Joined: 17 Jan 2004
Posts: 20
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| 17 Jan 2005 6:37 Re: noise in transient |
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| layes2 wrote: |
there is glitch in tran
just multipy the ac gain with the tran signal |
Hi,Layes2, Just multipy the ac gain with the tran signal. Can you tell me why?
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