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Old 25th August 2011, 03:47 PM   #181
Salas is online now Salas  Greece
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Hello guys. Is there an LT Spice directive to integrate a noise analysis spectrum that depicts density figures per Hz to an RMS total? Example, I wanna know what the attached represents in RMS as a 0.1Hz-10Hz total. Thanks.
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Old 25th August 2011, 04:28 PM   #182
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I found this set of commands on the LTSpice yahoo group. After the simulation has run, go to the error log, right click in the middle of the window and select "plot measured data". Then select the desired traces.

.step dec param x 11 10meg 10
.noise V(Vout) Vsine oct 100 10 {x}
.measure ns INTEG V(onoise)
.measure snr param -20*log10(ns)

Vout should be your output node for the amplifier, and Vsine should be your input source. I have not looked into this really, and don't know what other things can be done.

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Old 25th August 2011, 04:33 PM   #183
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Will try it and report back. Thanks.
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Old 25th August 2011, 04:42 PM   #184
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My error log has the plot data option in ghost form after I run the noise, is there something to prevent that?
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Old 25th August 2011, 05:17 PM   #185
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One step ahead, I solved that ghost thing. I can plot sn and snr.
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Old 25th August 2011, 05:35 PM   #186
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What does ghost form mean???

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Old 25th August 2011, 06:06 PM   #187
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Means it was gray, unable to click. But it was due to previous other directives messing that I switched off. I edited the directives to include flicker region up to 20kHz audio band. It changes nVrtHz to nV plot VS frequency, but I don't know, is that 20kHz point an RMS total to read?

.step dec param x 11 0.02meg 10
.noise V(Vout) Vsine oct 100 0.1 {x}
.measure ns INTEG V(onoise)
.measure snr param -20*log10(ns)
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Old 25th August 2011, 06:29 PM   #188
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You may want to change your Y axis to logarithmic. I'm pretty sure it's RMS, but I don't know for sure.

Here is the thread from the LTSpice yahoo group, for those with access:

Yahoo! Groups

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Old 21st September 2011, 02:35 PM   #189
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Default LTSpice and windows7

I've just started using LTSpice since my new 64bit PC wont let me run Circuitmaker. I'm trying to drop the required .INC file into my schematic, but cannot find the schematic files! Some computer geek I know says windows7 has this nice user friendly feature that hides a lot of files, so this may be a reason for my missing files. (Supposedly they do this to make it harder to pirate software).
So how can I create new models if I cannot find and open the files?
Anyone else have this problem and solution?
Thnx
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Old 21st September 2011, 10:01 PM   #190
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I have been successfully using LTSpice with Win7 for almost 2 years now. I hope you're a member of the Yahoo LTSpice User's Group at < LTspice : LTspice/SwitcherCAD III >.

I think your files aren't showing because the "*.mod", "*.asc", and "*.lib* filename extensions used as LTSpice defaults are associated with other programs; possibly even the operating system. The answer to your question goes something like this (see atch):
- Open the "Windows Exploder" (a.k.a. "File Mangler", or whatever it's called this year)
- Go to the top-level directory of "C:\"
- Select "Organize" > "Folder & Search Options"
- On the "General" tab, select "Show all folders" > "Apply"
- On the "View" tab, un-select "Hide extensions for known file types"
- Un-select "Hide protected operating system files"
(Yeah this makes it easier to do something stupid - like delete the O.S.)
- Select "Show hidden files, folders, and drives.
(May not be necessary. Sometimes the Installer seems to mark things as "Hidden" for no obvious reason.)
- Click "Apply", then "Apply to Folders"
- Go looking for your files. The default LTSpice installation directory is a good place to start, but I don't recall what the current default location is - probably somewhere under "Program Files" or "Program Files (X86)". On MY machine, I parked LTSpice at < C:\Applications\LTC\LTspiceIV >.

Dale

p.s. - As I recall, LTSpice is totally insensitive to filename extensions except for the "standard.*" libraries in < ..\LTSpiceIV\lib\cmp >. So you can use filename extensions like "Super_Circuit.exe", or "Opamps.Huge_Parts_Library", or "*.My_Awesum_Designs". Of course, some choices for filename extensions are more helpful than others.

p.p.s. - If you haven't found the Windows "Snipping Tool" yet, take a few minutes to play with it. It's much more versatile, and a lot easier than "PrintScreen".
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Last edited by dchisholm; 21st September 2011 at 10:18 PM. Reason: Removed redundant step
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