Top Ten:Circuit simulators

Hmm, what to do a Friday evening, maybe composing a top ten list with the top ten circuit-level simulators?!? Yeah! As for the layout tools I have tried quite a few of them and want to order them according to my liking. Once again, these are my personal views and I am quite happy to receive some feedback. Yet again, I will most likely also misuse the names on the tools from the different vendors, and will use the “common name” for it…

  • #10: pyCircuit

    I am starting off with a fairly recent contribution to the world of simulators. PyCircuit is a package available from a git repository and it has been partly developed by a friend of mine, Joacim Frisk. The package allows symbolic analysis and it covers the AC, DC, transient analyses as well as say PSS and PAC. It has an embryo for a gnucap (see #7) interface, i.e., it can read a gnucap netlist and run the simulations on it.
    I just want you to get some flavour on what’s going on out there… and the rest of the list is probably more known to you. I have only done some rudimentary trials with pycircuit.

  • #9: TINA-TI

    I continue the list with a tool I have never used … and once again I might not do TI (Texas Instruments) justice by putting their Spice simulator for windows last. However, it is for windows only and they do not provide the whole TINA-TI package for free. It supports AC, Transient, DC analysis, some Fourier analyses and a couple of steady-state analyses. If I get some time, I will evaluate the tool more (I just need a windows machine … or at least try over wine). As #5 does, they offer a large variety of free circuit descriptions to be downloaded from their home page.

  • #8: QUCS

    The quite universal circuit simulator (QUCS) is also a freeware and it is very fast to setup simulation and start crunching those numbers. Due to its GUI it is quite “educational” and a bit PCB-oriented. It has the basic simulator options and can handle veriloga code (and more). As we talk about the GUI, the cells are stored in an XML format and we once started to work on an XML parser to be able to port schematics/netlists between different tools … that is yet to happen.

  • #7: Gnucap

    Gnucap is also free, but requires some hands-on to operate and to “get into”. This hurdle and the fact that it is not that well maintained currently (or?) puts this after bullet #6. I put it high on the list, though, as it is associated with the gEda flow and is available in e.g. the ubuntu standard repositories. It does not have any “advanced” simulator options and we are “limited” to DC, AC, transient analyses (for now…) It enables us to do mixed-mode simulations.

  • #6: Ngspice

    I like ngspice! It is also free and fairly well maintained. It enables me to quite quickly go from a spice-format and run with a free simulator. Quite easily, I can kick of a large corner set using an unlimited amount of licenses. As for the other free simulators, it is a bit limited in terms of simulation options (does not contain periodic steady-state analyses, etc.). At home I use it quite extensively to test different ideas and it can be trimmed to simulate veriloga, etc. It handles BSIM4 and EKV models.

  • #5: LTSpice

    Linear Technologies actually enables us to use their spice simulator for free! Further on, it can be quite easily associated with the Electric layout editor and some of the other freeware tools such as the gEda package. In addition, Linear also provide a huge list of example circuits to download from their home page. LTSpice handles “all” transistor models.

  • #4: Pspice

    Cadence acquired the Pspice tool which was originally developed by Microsim. Unfortunately it is available on windows only 😉 but it is quite handy to work with as such. Now, professionally, I tend to have access to #1 and #2 on this list and therefore I do not really use #3 and #4 anymore.

  • #3: Hspice

    Synopsys acquired the Hspice simulator from Meta Software quite a few years ago. (I still have a Meta Software manual…) and it was also the first simulator that I used “professionally”. Back in those days we used the Led layout editor from which we generated the netlist, handhacked the bulk connections, hand hacked the testbenches, etc. We were quite immature and today I would have done it a lot differently…

  • #2: Eldo

    Eldo from Mentor Graphics takes a strong position and definitely competes with #1… As I joined Sicon Semiconductor I left the cadence-dominated world and got to work with eldo. It was a pleasant experience and I also enjoyed the script-based environment (kind of anti-gui) that we worked with. Yes, not really related to the simulator, but yet … I found that, at least some years ago, eldo had a much more robust way of going towards mixed-mode simulations. It could probably be due to the fact that in the netlist environment, it was easier to handle this than through the schematic/GUI of #1 on the list.

  • #1: Spectre

    Cadence is on the top again. Actually, I would probably put eldo here if it was not for a strange simulation error I got in one of my extracted cells some years ago. Unfortunately, we had to push out the tape-out due to this. I am still today not sure what went wrong… The two competitors for the top place are eldo and spectre. Since I mainly use spectre nowadays it ends up here. The simulator also gets credit for Ken Kundert’s work and his designer’s guide web page. Spectre also ends up high on the list now, as they have added transient noise, and dynamic sweeps to their portfolio…

So, any comments? What is your list? Please post your idea on the correct list.


22 thoughts on “Top Ten:Circuit simulators

    • Hmm, have actually not heard of that one. I have to download a trial version it seems (which luckily is available for linux). The trial version seems a bit limited though, and unfortunately the veriloga compiler is not included. Hope it supports several different file formats!

  1. Regarding #3, I too remember “those days”. Obviously there are better design flows today, but all that hand-hacking of HSPICE netlists was surprisingly efficient as I remember it now. I enjoyed using HSPICE.

    Nostalgia kicks in as I write this, and speaking of hand-hacking the bulk node, I remember doing the entire chip shown in my blog header without LVS [hear, o students of today … 🙂 ]. It’s a dual (I&Q) 8x time-interleaved 10-b pipeline ADC, and the only “LVS” available was to run a few clock cycles of the extracted netlist in HSPICE and see if it seemed reasonable.

    No one believes it today, but we also had to get up at 4.00 every morning and scrub the freeway clean using only a toothbrush, while being constantly hit by cars … 😉

    • Well, actually LVS is a bit overrated if you use the layout as your schematic entry …

      … we also had to get up at 4.00 every morning and scrub the freeway …

      Yeah?!?! Well, close to tape out, we had so much to do that I had to go up before I went to bed. Then I had to go to the university and place all transistors on the wafer by hand – using only an ice hockey stick and a roll of duct tape.
      For the digital circuits our system was so primitive that we only had 0’s to program with … and we were constantly hit by buses too.

  2. But I actually worked 36h non-stop to meet the tape-out deadline on that chip. That’s for real. We* ordered pizza to the university so the food breaks were minimized.

    *) If I remember it right, Dr. Christer Jansson was also working on a design of his own for the same tape out, and having him around was great moral support.

    And … this is for real too: Linköping had just been hit by the worst blizzard in memory, so to start that 36h shift I first had to wade in snow up to my hips at 5 am with the snow storm in my face all the way from Rydsvägen to the B-building on campus. It made me seriously mad but also determined to “win”, so it was probably a good thing even if it didn’t seem like that at the time.

    I’m sure there are more stories like that out there …

  3. Thank you for mentioning TI’s suite of design tools in your blog. I encourage you to try TINA-TI, I think you’ll find it one of the easiest circuit simulation tools to use. I know you said you don’t have Windows, however lots of people use TINA-TI under Wine in Linux and OSX. It also comes with a library of over 150 practical circuit examples and reference designs. In addition to the full suite of analog design tools in the Analog eLab, engineers also help each other with ongoing support through the TI E2E Community, an online engineering network, Stay tuned for new and innovative changes to our design tools later this year. Thanks again and I’d be happy to answer questions you might have.

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  6. Please consider:

    ViaDesigner is a mixed-signal simulator that includes:
    Schematic capture (multi-page & hierarchical)
    SPICE simulation
    HDL entry (VHDL & Verilog)
    VHDL-AMS (mixed-signal modeling)
    Mixed-language and mixed signal simulation: VHDL-AMS + Verilog digital for example.

    Plus ViaDesigner comes with a set of mixed-signal design wizards that accelerate the generation of useful circuits like: op-amps, programmable gain amps, TIAs, differential amplifiers, integrators, comparators, filters (continuous and switched capacitor), ADCs, DACs, sigma delta modulators, regulators, band-gap based bias generators,…

    ViaDesigner is available with a free 30-day evaluation. Monthly subscriptions start at $29/month for the MAKER version and $49/month for the Pro version.

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  9. I recently tried TINA 10 simulator from Designsoft. It was good in mix signal simulation. It handles Verilog.asm VHDL and SPICE. So far I have not a find a bug yet. For $1200 and it got both PCB layout package, schematic simulation in mix signal and 20K part library which is OK for my pocket. Cadence Pspice is good but out of my reach (for company is OK but not for me). Spectre or Eldo is for company business.

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