what really SPICE is?

Discussion in 'General Electronics Chat' started by PG1995, Nov 17, 2011.

  1. PG1995

    Thread Starter Active Member

    Apr 15, 2011
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    Hi :)

    So far I have used Multisim, Circuit Wizard, and Yenka simulation programs. Two or three days ago someone was lecturing on PSpice like what it is and how it's used. I was much confused after hearing the lecture because I had thought that I knew what PSpice etc is. I know that PSpiece is a software just like Multisim based on SPICE. To see part of the reason for my confusion you can check this Google doc which I found after googling "pspice programming ppt". It seems more like a programming language software than drag-and-drop circuit builder and simulation tool. What am I missing? I have always dragged and dropped the components such as resistors and batteries to create a circuit. Please help me with it. Thanks a lot.

    Regards
    PG
     
    Last edited: Nov 17, 2011
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Spice is very similar to Multisim and various other circuit simulators. It is a program that is simply made to simulate a circuit that you can draw, change values, etc. and seeing what it does without even building it. SPICE stands for "Simulation Program with Integrated Circuit Emphasis". It was developed by researchers at the University of California in the 1970s. It's purpose is to show values of the circuit over time. It is not much different from Multisim--it is simply another program that does (basically) the same thing.
     
  3. steveb

    Senior Member

    Jul 3, 2008
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    What you are missing is the long history of SPICE and computers in general. The earlier computers, at the time SPICE was being developed and used, did not have modern fancy interfaces. There were no graphics monitors, laser printers or even mouse input. You would use a keyboard and monochrome (typically amber or green) ascii only terminal display, tied into a mainframe computer. Early on, the baud rate for the terminal connection was only 300 baud, and when it finally got up to 9600 baud, people thought it was blindingly fast, and a great luxury. Output was typically sent to a wide-page dot-matrix printer.

    You would enter the circuit configuration by a netlist definition, which is still used by modern spice packages and PCB software today, although you don't see that part unless you look for it. The netlist simply defines the nodes and the interconnections of components in a simple way in a text file. A simple text editor was used to make the input file and then the spice command was typed on the command line (for example "SPICE INPUT.CIR").

    By the way, I'm just old enough and old-fashioned enough to still do my spice modeling this way. Some of us "die-hards" still value the old command line and have not abandoned it entirely. Feel free to laugh, and if you want an even bigger laugh, I can post a few pictures of my old slide rules. :p
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I would say that Spice is the core and Pspice is the graphical front end based on it.
    For example I use MicroCap from Spectrum soft, which to me seems to be based on Spice, at least in the history of it. The component models are Spice-like, the simulation properties are spice-like, but the gui and simulation setting menus are much easier to use than in pspice.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    Others have already stated this but I already wrote it so here is a sort of summary:

    Spice is the underlying software that performs the circuit simulation for most of the analog simulators available. In its basic form the input is a text file netlist. That is how Spice was used in its early days. Most simulator programs have a command allowing you to view this netlist, if you want.

    A graphic schematic interface, which allows drag and drop of components and easy circuit interconnections, is what PSpice, Multisim, LTspice, etc. uses to interface to the Spice simulator and that is what you are familiar with. That interface converts the schematic to the netlist needed for the Spice simulation. It's the differences in the graphic interface that mainly differentiates the various analog simulators. The underlying Spice simulator is very similar in most cases.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Crutschow you just said what I wanted to say but didn´t have the right words for it.
    All the programs I know use spice netlist and spice component parameters, even though they have different computational engines, they use the same basics, i.e. the same set of equations for the circuit. They probably use different ways to solve those equations, but the basics stay the same.
     
  7. DerStrom8

    Well-Known Member

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    I'm pretty sure Spice is the program, PSpice is the professional version, and LTSpice is the lite version.....
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    Very much like the old die-hards who wouldn't abandon DOS or Unix command line and move over to the Macintosh interface. (Windows came long after that).
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    For SPICE simulation back in the early 80s, we had Berkeley SPICE installed on a mainframe computer that was running the Dartmouth Time Sharing System (DTSS), and we used Digital Equipment Corporations' LA120 Decwriter III hardcopy terminals:
    [​IMG]

    They would accept 14-7/8" wide paper, and we went through LOTS of it.

    Some example font sizes it was capable of printing:
    [​IMG]
    [​IMG]

    When I started with it, we were using 110 baud acoustically-coupled modems like this one:

    [​IMG]

    We thought we were in heaven when we finally got 1200 baud. 9600 baud was so fast, we thought we were going to wear out the Decwriter in no time. That printhead was really rockin' back and fourth. ;)

    The GUI (graphical user interface) used nowadays as a front-end for the underlying SPICE engine makes it soooo much easier than it used to be; but sometimes you still have to dig "under the hood" to get the results you're looking for.

    While I suppose that I could go back to that, I really wouldn't want to - it would simply hurt my productivity too much. With the GUI interface, I can slap together a simulation pretty quickly and at least get a ballpark idea of where things are. If I were having to type all that stuff in, or even copy/paste it together from library text files, it would take me quite a bit longer.
     
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  10. PG1995

    Thread Starter Active Member

    Apr 15, 2011
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    Oh man! After reading some of the replies, especially that of Steve and Sgt. I'm happy I wasn't born back then!:)

    I don't really understand the use of bold part "Simulation Program with Integrated Circuit Emphasis". What kind of special emphasis on ICs? Most integrated circuits are dealt in programs such as Verilogger or Modelsim which don't have anything to do with SPICE. Could you please explain it a bit?

    Thanks a lot everyone for your replies. Your guys are really nice and kind.

    Best wishes
    PG
     
    Last edited: Nov 17, 2011
  11. steveb

    Senior Member

    Jul 3, 2008
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    SgtWookie, ...

    Ha, thanks for posting those memory jolting pictures.

    Yes, I can see that with your highly prolific nature, doing it by the old ways is too cumbersome. I'm a slow turtle that doesn't mind the old pace because I don't do spice modeling too often. I have to say that I would not want to go back to the old computer processing power because then our productivity would really plummet. :p
     
  12. steveb

    Senior Member

    Jul 3, 2008
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    Don't forget that back then, ICs were sometimes a handful of transistors, caps and resistors wired up into an opamp configuration or other simple circuit.
     
  13. PC Pete

    New Member

    Nov 11, 2011
    10
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    FWIW, I still have a fully working CP/M system, complete with SASI controller, a massive twenty MEGAbyte disk drive (wow!), and a HP 900 terminal (that runs at 38,400 baud!!). I don't know why I keep it, I just can't bring myself to throw it away.

    In fact, it's fun to bring up CP/M 2.2 or TurboDOS and play with Turbo Pascal, DBASEII, etc. But only from time to time.

    It did have a very early circuit modeling program on it, based on something very similar to SPICE, but that directory cluster has gone to the great magnetic home in the sky.

    Luckily, I can still play LADDER.COM, Zork, and even dial up a few remaining BBSes on the Smart Automatic Modem (v.24, 2400 baud, thank you very much!) ;)
     
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