Ltspice simulation Unknown parameter "*" error

Question

I gave my circuit that I simulated, it gives me Unknown parameter "*" error, as far as I learned the multiplication can not be made due to time varying quantity which is d source in the circuit. enter image description here

But exact circuit is working shown in the 2'nd picture. How should I write my parameters to make it work for time dependent?

enter image description here Above image from answer to " Control to output transfer function " by @Verbal Kint, edited by @Mhan and posted on Electrical Engineering Stack Exchange is licensed under CC BY-SA 4.0.

The error is given as below:
enter image description here

Answer 1

The main issue here is that you're using a V source where the book uses a B source. V sources can't have any dependency on non-constant parameters like V(d) or I(Vil); you have to be able to predict the exact output of a V source without even knowing other nodes exist.

A B source, on the other hand, can output an arbitrary function of constants and other quantities in the circuit. This power comes with a drawback: overuse or misuse of B sources can make the simulation run slow or fail to converge. This simple setup should be fine, however.

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Separately, if you were able to use a V source, you can't enter its value as simply {a}*{b}; LTspice doesn't know what to do with a * in a V source if it's outside of curly braces. I think (but don't remember exactly, and the computer with LTspice installed is at work) you need to write it as {a*b}, but it's possible it needs to be {{a}*{b}}. I'm pretty sure the latter is the PSPICE way of writing it, and that LTspice will accept either.

• Mhan: Hello thank so much for your valuable comments, I tried your curly braces solutions, they didn't work, I think I need to use B source in this case right ? @Hearth
• Hearth: Yes, for what you are doing you need to use a B source. The modifications I listed for the curly braces would only work if all quantities used are parameters, not measured values (so {vin*v(d)} is still not allowed).

Answer 2

You need to change V3 to a B-source, that will fix the problem. B-Sources are custom voltage sources that can have functions and equations.