Update on SPICE Electric Circuit Simulations

[snip]

Whatsamatta... did your virgin get away ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | America: Land of the Free, Because of the Brave

"Ir. Hj. Othman bin Hj. Ahmad" schrieb im Newsbeitrag news: snipped-for-privacy@e65g2000hsc.googlegroups.com...

Hello,

I wonder what you did. LTspice is one of the most compatible SPICE programs on a netlist level.

Many universities have switched to LTspice. The main reason is that LTspice is a free, fast, and unlimited SPICE simulator. This allows any student to simulate even the most complex circuit.

Are you aware that maybe 100000 people had managed to use LTspice for their SPICE simulations?

LTspice recognises the ".AC" comamnd line of course. Please send me your LTspice schematic(.asc) and/or your LTspice netlist and I will tell you what you did wrong.

Best regards, Helmut Moderator of the LTspice Yahoo group

TINA-TI has another limitation too. It doesn't have E, F, G amd H sources in their schematic entry.

I'd think you'd be using 3F5? I'd be hard-pressed to still find a FOTRAN or RATFOR compiler these days. :-)

This isn't really true. Sedra & Smith, which is the textbook I used in college, had plenty of SPICE stuff in it back in the early '90s and the current version has even more.

I suppose so, but most people coming out of college today are neither expert circuit designers nor expert SPICE modelers -- and becoming a really good SPICE user is generally far less demanding than becoming a really good designer.

LTSPICE is quite compatible -- it sounds as though you didn't peruse its instruction manual?

How so? My experience is that ORCAD *Capture* is quite simple to use, and I

*wish* it had more sophisticated features (and fewer bugs).

Yes. If you'd doing mixed analog/digital simulations, there's XSPICE or VHDL-AMS or Verilog-A -- what you end up using is often driven by what models are available.

If you're going to be shipping any of your designers over here to the U.S., Verilog is quite popular as well.

Mmmm... it's been ongoing deveopment for some decades now...

With what tool? Some are a lot buggier than others...

I think one can make a pretty strong argument that the old text editor/command line SPICE/post-processor graphing utility approach to circuit design is -- in

*most* cases -- not as effficient as the contemporary schematic capture/simulation/plotting "all in one" tools most people now use.

Feel free to start patching the source code yourself? :-) I mean, your statement is really too negative -- there are plenty of reliable, reasonably unlimited SPICEs that are used for real designs every day. It's true that if you're looking to do a modern IC design, yeah, good luck finding a 100% free design flow from SPICE to layout/DRC, but it's not like anyone's going to fab your design for free anyway, you know? There are universities that have older (donated) fab equipment and do have students design complete ICs along the lines of op-amps, logic gates, small ADCs/DACs, PLLs, etc., and this is quite valuable. The more common (it would seem) approach of universities using commercial software that's provided for free or heavily subsidized and using services such as MOSIS to do the IC run seems to work fine too: Thousands of new students make ICs every year, after all.

Not true. I don't think you'd find a major US university today where students don't use SPICE in a EE curriculum.

That's a start, but you're never going to be able to design decent op-amps if you haven't gone through a fair amount of analyzing circuit performance using loop analysis, phasor or Laplace domain techniques, etc. If you only know Kirchoff's laws and have a SPICE simulator, I just can't you ever suddenly coming up with, e.g., a Gilbert cell mixer or a Doherty power amplifier or even many of the fancier current sources out there.

---Joel

I think it's much more important to learn the basics. These days, there's a lot of information to take in during a 4 year period university term. This time is better spent learning basics. It's surprising how many engineers, coming out of the university, have a poor grasp of utilizing Ohm's Law when analyzing practical circuits. Spice is a valuable tool, but without a good grasp of the basics, Spice can produce misleading results. If the practitioner can't do the necessary paper or mental calculations to verify Spice results, this person is not valuable to employers.

Many universities teach Spice basics, as evidenced by the number of Spice tutorials on the web from universities. To become proficient in Spice requires time, not necessarily in learning Spice, but becoming proficient in dealing with the analysis of semiconductor devices. The

4 year university curriculum does not allow for this level of expertise and/or students learn enough to pass the test without understanding practical applications of what they learned.

LTspice is very compatible with standard Spice syntax. I feed LTspice ASCII decks without problem from our filter programs and from PSpice decks. Yes, LTspice is nearly 100% PSpice syntax compatible. Post your deck and I'm sure someone can show you what your problem is. The other responders to your post are all proficient in Spice.

--
Mark

I wouldnt touch spice with a barge pole !

If you add in stray capacitance, inductance, enclosure, spread of components then SPICE simply is useless.

I believe it is YOU who is useless ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | America: Land of the Free, Because of the Brave

Some that don't: Allen and Holberg -- isbn: 0195116445 Jakob Baker --

But you need to know what buttons to push in which sequence. Did you walk right out of your mother?

Kirchoff is tought in all junior electric classes. Then abandoned because there is SPICE. But it is still expected that the student know how Kirchoff works. When did you study? in the 60's? Did you study?

In your analysis, I think you forgot to mention gnucap

If you have capabilities in computer simulators, I think you should subscribe to the mailinglists mentioned there, or go to the gEDA pages at geda.seul.org and subscribe. You can do a lot more good to electronic engineering if contributing to free and open source than to post comparisons like the one you did here.

-- Svenn

-- Svenn

Ahmmmm.......you are obviously a little unfamiliar with the capabilities of spice, and how 10,000's of analogue designers actually use spice to design in the pure virtual world, 10,000 transistor analogue circuits that work right first time. Modern analogue ic design is quite impossible without spice. No one in the i.c. world designs with real components. This is a fact.

It is a little naive to suggest that modern design tools do not deal with aspects such as component variations and parasitic effects. Professional spice tools have many completely standard features to deal with such issues. To wit, Worst Case Corner model and Monty Carlo analysis, and parasitic extraction. Today, the models themselves are usually amazingly accurate.

So, if it costs $100k for a mask set, just how do you imagine you are going to experiment with the real thing in order to produce a design?

--
Kevin Aylward
www.anasoft.co.uk
SuperSpice