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20th November 2017, 10:13 PM  #11  
diyAudio Member
Join Date: Feb 2004
Location: Austin, TX

Quote:
So, when I want to derive the frequency domain ("s" domain) input/output relationship of an RLC circuit, for example ... with nonnumerical symbols (like R1, L3, C2) instead of specific values (1 kohm, 3 mH, 5 uF) ... i still do it by hand pen and paper baby !!! 

20th November 2017, 10:26 PM  #12 
diyAudio Member
Join Date: Dec 2015
Location: Newfoundland

This is beyond my skill level. Every time I ask a question on this forum, I realize that I know less than previously thought. Eventually, I might realize that I know nothing!

20th November 2017, 10:45 PM  #13 
diyAudio Member
Join Date: Apr 2011

Maple, and MATLAB with an added toolbox, can do symbolic math.
https://www.maplesoft.com/products/m...mericmath.aspx Symbolic Math Toolbox  MATLAB 
20th November 2017, 11:08 PM  #14 
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Join Date: Jun 2002
Location: USA, MN

SapWin Nuova pagina 1
you're welcome
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21st November 2017, 12:56 AM  #15  
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Join Date: Feb 2004
Location: Austin, TX

Quote:
Quote:
Seriously ... thanks for the links! Worth looking into 

21st November 2017, 04:11 AM  #16 
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Join Date: Jun 2003
Location: Maine USA

The early SPICE papers are available online
here and here. They give some insight into how SPICE does it. However KCL and KVL (node analysis) are the key to ANY electrical calculation. Details differ: sometimes it is easier to work in conductances than resistances, etc. That's just flipping the fraction over. The main difference between handcalculation and SPICE is that a computer does math thousands of times faster than a human. So the computer may not set up a full analysis, it can just tryandsee. As I understand it, at some level of complexity, SPICE may assume the midpoint of a network is "half" the battery voltage. Then it computes all the currents and adds them up. By KCL they should sum to zero. They don't? Then SPICE adjusts its "half" guess, a little or a lot depending how far out it was, and does all the calculations again. In around a dozen to a hundred iterations it narrowsin on the "right" answer to 8 decimal places. (I may handcalc 3 iterations to get 2 places, which is good enough for most work.) Nonlinear elements are represented by a formula which is recomputed for each iteration. .TRAN analysis does all that manymany times over the specified time interval. There's original FORTRAN SPICE, a C SPICE, and many folks who sell packages which include SPICE and typically with extra smarts (SPICE was put together quickly, so decades of smart programmers leads to little improvements). Last edited by PRR; 21st November 2017 at 04:16 AM. 
28th November 2017, 02:07 PM  #18 
diyAudio Member
Join Date: Oct 2005
Location: near Stuttgart, south Germany

In a previous life as a student, we had to program the underlying
algorithms ourselves ( in isolation, not everyting together) for educational reasons b4 we were given access to spice. We used this book : < Computer Aided Network Design: Amazon.de: Donald Calahan: Fremdsprachige Bucher > and this one < Circuit Theory: A Computational Approach: Amazon.de: Stephen W. Director: Fremdsprachige Bucher > The second one contained an awful lot of typos and misprints, looks like Wiley could not afford a lector. :( In concept, it was excellent, but unusable without a buglist. I bought that stuff in Nov. 76...
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