OK 
I'll keeping looking in throughout the day hopefully.
If you do try an example then I would suggest the first thing you do after opening it is to rename it and save it somewhere else. That keeps the originals intact and then you can play around as much as you want with the resaved version.
I'll keeping looking in throughout the day hopefully.
If you do try an example then I would suggest the first thing you do after opening it is to rename it and save it somewhere else. That keeps the originals intact and then you can play around as much as you want with the resaved version.
Attachments
That's very good of you. I really appreciate your help. As someone remarked on a previous thread "diyAudio is one of the internet's greatest resources". Having started out as a teenager in 1959 with my first audio amp and finding it difficult to get to grips with circuit simulation, I couldn't agree more. No time like the present to get up to speed on the subject - I'm confined BY LAW to the house because of my age. Many thanks.OK
I'll keeping looking in throughout the day hopefully.
If you do try an example then I would suggest the first thing you do after opening it is to rename it and save it somewhere else. That keeps the originals intact and then you can play around as much as you want with the resaved version.
Try different opamps / models.
The ADA4898 model for example seems somehow broken, even the newer version ( ~1 year old).
The old model had the noise response _completely_ wrong, among other things.
Funny, for a chip whose selling point is noise.
The current version has corrected that when I use one ADA4898 only.
When I use two of them, it usually cannot find the operating point or the simulation crawls.
When I replace one of them with a LME49860, it works. It doesn't matter which one.
I even had transients in completely unrelated parts of the circuit that had ground as the only
connection when the op amp input went through 0 last week. Weird. Impossible to happen.
I have the impression that TI models like LME49860 or THS4021 feature less surprises.
Cheers, Gerhard
The ADA4898 model for example seems somehow broken, even the newer version ( ~1 year old).
The old model had the noise response _completely_ wrong, among other things.
Funny, for a chip whose selling point is noise.
The current version has corrected that when I use one ADA4898 only.
When I use two of them, it usually cannot find the operating point or the simulation crawls.
When I replace one of them with a LME49860, it works. It doesn't matter which one.
I even had transients in completely unrelated parts of the circuit that had ground as the only
connection when the op amp input went through 0 last week. Weird. Impossible to happen.
I have the impression that TI models like LME49860 or THS4021 feature less surprises.
Cheers, Gerhard
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Mooly's tutorials are good, if you work through them you'll have a pretty good understanding of LTSPICE. Also take a look at ltwiki.org, the analog.com website and youtube page, and google "ltspice college course" for online courses. Finally if you want to spend some money, Wurth has an excellent LTSPICE book, among others.
tommost
tommost
Great, thanks for those suggestions. I'll start fresh into the learning curve tomorrow.
Excellent
well done.Don't forget there is a kind of instruction book within LT but its a bit hard going tbh at times. Just select 'Help' on the top line and then 'Help Topics'.
Attachments
I am still playing with different AC analyses, but I'm always missing the ;op character. I think I saw it a while back, but it no longer appears. I have completed a FFT successfully without it. Could it have disappeared out of the window? I have seen other symbols wander off almost out of sight, and had to struggle to get them back. I am using the latest version on Windows 10.
Are you attaching the .op command to the workspace?
When you right click the workspace for the first time you should select 'Edit Simulation Cmd.' and then click 'DC op pnt' and then click OK.
Having done that the .op command should be attached to the cursor ready for you to place anywhere on the workspace by left clicking when it is where you want.
When you right click the workspace for the first time you should select 'Edit Simulation Cmd.' and then click 'DC op pnt' and then click OK.
Having done that the .op command should be attached to the cursor ready for you to place anywhere on the workspace by left clicking when it is where you want.
Great thanks. I had forgotten its significance after moving on to AC simulation. I did not save the file. (I think that's what happened anyway).
I'm sorry, but I think it should be here, this is also posted at
https://www.diyaudio.com/forums/software-tools/316534-ltspice-limiting-decimals-2.html#post6144735
These functions limit the length of a figures to a set length independent of the exponent while at the same time rounding the number.
0.000012345 -> 0.0000123 (when 3 significate figures requested)
0.000012366 -> 0.0000124 (when 3 significate figures requested)
1234.500000 -> 1230 (when 3 significate figures requested)
1236.600000 -> 1240 (when 3 significate figures requested)
works also for other numbers.
Frans.
;================================================= =============================
; === FdWs Rounding functions by Frans de Wit for Signature Origin (diyAudio.com)
; === Truncate round to a fixec fixed number of figures
;================================================= =============================
;V=round(v(inp,inn)/(10**floor(log10(v(inp,inn))-2)))*(10**floor(log10(v(inp,inn))-2)); B-source formula for 3 figures
;V=round(v(inp,inn)/(10**floor(log10(v(inp,inn))-5)))*(10**floor(log10(v(inp,inn))-5)); B-source formula for 6 figures
.func rndx(a,x) {round(a/(10**floor(log10(a)-(x-1))))*(10**floor(log10(a)-(x-1)))}; Function for x figures
.func rnd3(a) {round(a/(10**floor(log10(a)-2)))*(10**floor(log10(a)-2))}; Function for 3 figures
.func rnd6(a) {round(a/(10**floor(log10(a)-5)))*(10**floor(log10(a)-5))}; Function for 6 figures
https://www.diyaudio.com/forums/software-tools/316534-ltspice-limiting-decimals-2.html#post6144735
These functions limit the length of a figures to a set length independent of the exponent while at the same time rounding the number.
0.000012345 -> 0.0000123 (when 3 significate figures requested)
0.000012366 -> 0.0000124 (when 3 significate figures requested)
1234.500000 -> 1230 (when 3 significate figures requested)
1236.600000 -> 1240 (when 3 significate figures requested)
works also for other numbers.
Frans.
;================================================= =============================
; === FdWs Rounding functions by Frans de Wit for Signature Origin (diyAudio.com)
; === Truncate round to a fixec fixed number of figures
;================================================= =============================
;V=round(v(inp,inn)/(10**floor(log10(v(inp,inn))-2)))*(10**floor(log10(v(inp,inn))-2)); B-source formula for 3 figures
;V=round(v(inp,inn)/(10**floor(log10(v(inp,inn))-5)))*(10**floor(log10(v(inp,inn))-5)); B-source formula for 6 figures
.func rndx(a,x) {round(a/(10**floor(log10(a)-(x-1))))*(10**floor(log10(a)-(x-1)))}; Function for x figures
.func rnd3(a) {round(a/(10**floor(log10(a)-2)))*(10**floor(log10(a)-2))}; Function for 3 figures
.func rnd6(a) {round(a/(10**floor(log10(a)-5)))*(10**floor(log10(a)-5))}; Function for 6 figures
12 KHz FFT
I think I've mastered the the technique of performing a FFT. To get it to work properly needs great care, as it is far too easy to mess up the calculations. The calculator and a notepad and pen are quite useful for me. I did this one at 12 KHz, extrapolating the settings used for 4KHz on page 2 in the tutorial. I left the two capacitors' value at 1μF. I wonder does the result make any sense. It took 30 minutes on a reasonably fast machine to compute.
I think I've mastered the the technique of performing a FFT. To get it to work properly needs great care, as it is far too easy to mess up the calculations. The calculator and a notepad and pen are quite useful for me. I did this one at 12 KHz, extrapolating the settings used for 4KHz on page 2 in the tutorial. I left the two capacitors' value at 1μF. I wonder does the result make any sense. It took 30 minutes on a reasonably fast machine to compute.
