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Old 1st March 2012, 11:54 PM   #1101
tvrgeek is offline tvrgeek  United States
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I get the same error if I use ".subckt" or not in the edit window for the model name.
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Old 2nd March 2012, 01:12 AM   #1102
keantoken is offline keantoken  United States
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The line ".subckt ecf10n20.txt" doesn't make sense. Think about it.
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Old 2nd March 2012, 03:21 AM   #1103
keantoken is offline keantoken  United States
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Try this. You are not following my directions in the first place. It looks like you are trying to follow someone else's directions. I too tried to do this ridiculous stuff and constantly had trivial, aggravating problems; I found an easier and simpler way and never needed anything more. It is convenient to have the subcircuit in your schematic directory anyways, so you can zip it up and send it to someone else like this.

When using models like this make sure the pinout of the model matches the pinout of the transistor.
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File Type: zip MOSFETModelTest.zip (2.2 KB, 44 views)
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Old 2nd March 2012, 04:50 PM   #1104
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by keantoken View Post
The line ".subckt ecf10n20.txt" doesn't make sense. Think about it.
Makes sense to me, but not to LTSpice. Deleting the line worked.
I am using the primer done by Laurier in Canada. It was making me think I needed to build a dedicated three terminal icon for the model instead of the supplied "M". There was another electronics forum with explicit steps that included the .subckt line in the parameters box.

The problem is all the instructions are written by folks who know how to do it. What you were saying was obvious to you, but not quite to me.

I was looking at the libraries that came with SIMetrix. They have a lot more old parts. Now I get the idea, I will try to link them. Old parts as I am reverse engineering old amps.

Much thanks. I hope my next question is harder.
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Old 3rd March 2012, 01:42 AM   #1105
keantoken is offline keantoken  United States
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Be careful about the old models, verify every one you use. You may find they are not even modeling the right transistor!
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Old 3rd March 2012, 03:44 PM   #1106
tvrgeek is offline tvrgeek  United States
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Sage advice. Models seem highly variable. Even for relatively simple things like a diode.

Today's question. Playing with the FFT function. I would have guessed the generator to be a mathematically perfect sine wave. This does not seem to be correct as measuring the output of a "perfect" source into a resistive load shows harmonics only about 80dB down. Any tips on size and windows when working in the 1 to 100K Hzrange?
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Old 3rd March 2012, 03:54 PM   #1107
jcx is offline jcx  United States
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a unobvious Ltsipce specific problem is that data compression for output files is the default setting

you have to add ".option plotwinsize=0" to every high resolution sim

then t_max_stepsize needs to be set in .TRAN to as small a value as needed by your analysis - be quided by test signal frequency, loop gain intercept, device ft

10 ns isn't too small - millions of points in the output raw file are "reasonable" with today's PCs

for very complex circuits, long sims you can restrict the number of nodes, currents saved
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Old 3rd March 2012, 04:01 PM   #1108
jan.didden is online now jan.didden  Europe
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Quote:
Originally Posted by tvrgeek View Post
Today's question. Playing with the FFT function. I would have guessed the generator to be a mathematically perfect sine wave. This does not seem to be correct as measuring the output of a "perfect" source into a resistive load shows harmonics only about 80dB down. Any tips on size and windows when working in the 1 to 100K Hzrange?
I see the same with a completely other product, the Labcenter VSM simulator. Source has pronounced 2nd and 3rd on FFT, yet the output of the circuit is much less and seems OK.
I haven't been able to find out why that is.

jan
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Old 3rd March 2012, 04:28 PM   #1109
jcx is offline jcx  United States
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not a problem in Ltspice with good settings

10 ns max step size, plotwinsize=0, default fft settings gives -180 dB numerical noise floor with 10 KHz sine, 2ms sim

selecting Blackman window function in the fft helps with settling time "tilt" of the fft noise floor, just saving the final few ms after a settling time can be done with .TRAN settings or in the fft dialog window

Last edited by jcx; 3rd March 2012 at 04:34 PM.
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Old 3rd March 2012, 04:46 PM   #1110
tvrgeek is offline tvrgeek  United States
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Which window is preferred in this tool? Hamming? Blackman? Hamming seems to invert some things.
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