Wednesday, August 21, 2019

spice models valve, tube, jfet with link to calculator

The question asked was can we model valves in spice. The answer is yes. Next question, will it be like jfet? Let's take a look at a couple models of each.


 If you have a tube manual you can compare the curves and make changes to produce a better match. The better approach is to find a model made by someone else.



 I used the same jig but had to change the voltages and polarity to match the jfet. One of these I did create because I couldn't find a model on line.
For valves you can have a little fun, as playing a video arcade game with this program.

The top view is loaded with a diagram from the tube manual. The bottom is the spice response to the model. You get the number from the datasheet and enter them in the boxes. Click plot and hope for good results. a little tweaking of the numbers may make the response better or give you a reason to start over. This program can be downloaded here:
Valve model calculator


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