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#1 Nov 24, 2020
veek
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Joined: 2020-11-24 01:17

Multiple-input controlled sources and Tuinenga SPICE book pg27

(briefly how is he getting k8.v2.v3 in the images)

He's trying to use POLY(dimension) to model a source using a polynomial to represent it. Form of Poly is k0 + k1x + k2x^2 and so forth so.. how the heck has he got k8*v2v3? If v1 v2 v3 are elements/dimensions of x the vector then x*x is the cross product and therefore.. you would get

k0 + k1(v1, v2, v3) +k2(v1,v2,v3) x (v1,v2,v3) and so on.. 

If on the other hand he's doing (k0v1, k1v2, k2v3) to represent his vector then how does k7 enter the picture

(if the Q is too simple for this place could you point me elsewhere - more suitable location)

Wed, 2020-11-25 11:43
oldmouldy
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A POLY source allows an arbitrary number of inputs and an arbitrary number of powers so things quickly become complex for multiple inputs and multiple powers.

For the simple case of one input, the POLY provides a Constant, the input variable (linear), the input variable squared, then cubed, and so on.

When there are two inputs, there is the Constant term, the linear terms, the squared terms, the cubed terms and so on.

For the three inputs case, again there is the Constant term, the linear terms (the inputs), then the "cross terms" for the products of each pair of inputs from the three inputs (the "squares"), then the "cross terms" for the products of each of the combinations of inputs to form the "cubes".

As the document states, for many inputs this rapidly gets error prone and, unless the formula really requires many of the terms, there are usually easier ways to sum the values together to get the required result.

Wed, 2020-11-25 13:01 (Reply to #2)
veek
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the basis for the math is Linear Algebra: any link/src/book for further reading that would explain what he's doing? (reread Strang?)

Tue, 2020-12-29 09:58
brendanalexis
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