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What is 'MNA', please?

On Mon, Mar 10, 2025 at 09:03 AM, Andy I wrote:

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But does it start with initial voltages, or with initial currents, as the first step?? I can't even say that much.

From the fact that the MNA system is based on node voltages as unknowns (including currents for voltage sources) and there exists the .NODESET directive for node voltages to aid NR convergence, I believe the first NR iteration is done using hints (or zero) for devices'voltage.

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Carlo.

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On 3/4/25 12:36 PM, Carlo wrote:

I've no idea why their ITS solutions are so different though...

* Heater model
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* Can be operated from AC or DC power sources.
* NB: When operating from DC power sources, "Skip initial transient
* solution" must be checked, to make use of this model.
*

You can beat your brain in as much as you want but you might want a different model. Maybe even the NH12AU7 model which doesn't include the heater.

Connect the LM317 to a resistor stand in for the heater.

--

David Schultz
"The cheeper the crook, the gaudier the patter." - Sam Spade

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So I tried. You can't use the word 'schematic' in a question without uploading a schematic! This is not sensible. I worked round it by writing 'circuit diagram' instead. Three cheers for British English!

Thanks, Tony. I will try.

On 2025-03-10 12:50, Tony Casey wrote:

You have to start a discussion and title it "Feature Request, or similar.

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Regards,
Tony

On 10/03/2025 12:51, John Woodgate wrote:

It is black if the background is set to white, as I have it, but the default background is black. The white dots are no more visible. How do I ask ADI to consider a larger dot option, or a grid option? I looked on EZ, but I don't see anything but discussions.

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Thanks, Tony. I will try.

You have to start a discussion and title it "Feature Request, or similar.

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Regards,
Tony

On 10/03/2025 12:51, John Woodgate wrote:

It is black if the background is set to white, as I have it, but the default background is black. The white dots are no more visible. How do I ask ADI to consider a larger dot option, or a grid option? I looked on EZ, but I don't see anything but discussions.

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You have to start a discussion and title it "Feature Request, or similar.

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It is black if the background is set to white, as I have it, but the default background is black. The white dots are no more visible. How do I ask ADI to consider a larger dot option, or a grid option? I looked on EZ, but I don't see anything but discussions.

On 10/03/2025 11:42, Alan Pearce via groups.io wrote:

I thought there was an option to change the dot size, but maybe there isn't. Don't have a copy handy to check at the moment.

No there isn't, but there is an option to set the dot colour, but I think the default is black, anyway.

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Regards,
Tony

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I thought there was an option to change the dot size, but maybe there isn't. Don't have a copy handy to check at the moment.

No there isn't, but there is an option to set the dot colour, but I think the default is black, anyway.

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Thanks for providing this case. In a nicely condensed form, it demonstrates the problems of legacy LTspice and how they are addressed by 24.1.

You have two models:

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.model 0 AKO: BSP89
.model 1 AKO: BSS145

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and the line

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M1 D G 0 0 {M}

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Legacy LTspice (aka the version that you assumed "works") interprets the the second "0" as the model name. That's because there is a model with the name "0" defined. However, the actual intent for this "0" is to label the substrate node. (As documented in the help.) It then goes on and finds "{M}" which resolves to "0". This is interpreted as a parameter to M1, but a single "0" is not a valid parameter. It keeps going, at the end you get a visible error message in the log:

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Error on line 4 : m1 d g 0 0 ?0?
? ? Error: ?No unlabeled parameter permitted for MOSFET's

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If you changed the M1 line into:

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M1 D G 0 1 {M}

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you'd expect the substrate node to be connected to node "1" and model "{M}" be used. Instead, legacy LTspice will use model "1" and again ignore "{M}" as invalid parameter. Still, it keeps going.

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LTspice 24.1 behaves in exactly the same way, except that it aborts with a hard error and a much better error message. This is the only acceptable behavior, because there is no point running a sim that obviously doesn't work out as the user intended.

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All this boils down to the fact that the spice netlist format is poorly designed.

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LTspice 24.1 introduces string parameters and thereby eliminates the need to name models like numbers, thus greatly reducing the likelihood of problems.

I understand your desire to add more features and improve performance. But I worry about backwards compatibility and portability. I am concerned that this is the tip of an iceberg of broken models. I haven't had the time check very many, but I know that quite a few long standing examples in the Files area of the group website are now broken because of the line-by-line syntax checker we discussed in the thread beginning #158931.

Adding new features to 24.1.x to address "problems of legacy LTspice" also introduces forward compatibility issues for people still using older versions of LTspice. There are lots of corporate users of LTspice who are not able to update to the "latest version" because of permissions restrictions placed by IT departments. This is a declining problem, but it still exists.

I am happy for new features and "improved" syntax to be added, but you should consider alongside this, "compatibility options", preferably at schematic level by directive so that "old" syntax remains acceptable. This is a common feature of compilers and Windows itself (even if 16 bit code cannot run any more, if anyone can still remember that).

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Regards,
Tony

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Thank you.

What I meant to say is of course "lasso one of the anchor points", depending on the direction in which you want to enlarge the rectangle.

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Ryu

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Thanks, Andy. I have to print to .JPG, and doing that directly from LTspice doesn't produce a good output, so I Print Screen and copy to Irfanview, crop and print from there. I think I will ask for an option to make the dots actually visible.

On Sun, Mar 9, 2025 at 06:07 PM, John Woodgate wrote:

1. I have the background colour for both schematics and waveforms set to white, because that saves a lot of toner when printing out.

The on-screen background color does not affect the printed output, in my experience.? That is true whether or not I have "Print Monochrome" selected, at least when printing to PDF.? I suppose Your Mileage May Vary.

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I wonder what I should see, with the grid enabled.

For schematic grids, you should see dots, not lines.? They are so tiny, I can barely see them.? Changing the on-screen colors does not seem to help me see them better.? Perhaps LTspice uses a size of 1 pixel, making them less apparent with high-res displays.? As far as I know, the schematic grid dots are on-screen only, not in the Printed output.? As you might notice (if you can see them), the on-screen dot spacing is not the functional grid spacing when you zoom out.? That is, it may show you one grid dot for every 2 or 4 or X functional grids - presumably so that the screen does not become filled with dots.

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In contrast, the waveform grids are dotted lines, and they are much more visible.? I have to tone-down their color so that they don't overwhelm the waveform lines.

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Andy

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