Hi Jim,
What do you think of LTSpice? I know why you need the Cadence package. But LTSpice comes with a schematic entry that offers a hierarchy structure which you mentioned before as very important (and I agree with that).
Regards, Joerg
I think LTSpice is fine, although I have misgivings about Mikey's twiddling of gmin, and other tricks that enhance speed but don't yield waveform-match to what I see in PSpice Probe.
I think Mark ("qrk") recently ran a chunk of their sonar chip on LTSpice and saw some bizarre results.
...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 |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Hi Jim,
Thanks, Jim. I just downloaded LTSpice, having only had exposure to PSpice before. It does seem to allow the usual step setting so maybe these kinds of trade-offs can be avoided. What I was surprised about is the fairly large number of netlists it supports if you want to use the schematic part as the point of entry on projects.
Regards, Joerg
The example circuit is 16Bit-AD-DA.sss.
As an exercise, see if you can decipher the method of the AD. Hint: instantaneous successive approximation. I might post a detailed circuit of the method, if I can around to it.
The reason I decide to make them was investigating modulating the power supply of RF transmitters. One wants to make the supply track the envelope of the modulating signal to get the efficiency up. So one goes A/Ds to D/A directly, which seems quite daft initially! The DA switches little floating PS (say Transformer with diode cap) in a series/bypassed fashion. The final output is the filtered quantised input used as a PS to the TX, with low loss. The idea being that one is only limited by the raw switching speed of the dac'ed PS. A PWM is going to have trouble at say, 50Mhz modulation frequency.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
In article , Jim Thompson wrote: [...]
In discrete land, getting matched sets does this too but it costs like the dickens. I've had R-packs made to get the tight ratio match needed it turned out to be the less expensive option.
Yes, and of them it depends on the ratios that are an easier match.
The trouble starts when the parameter you are trying to control is frequency. It is hard to get frequency to depend on a parts ratio. This is a big part of why almost everything is fed into a DSP these days. The DSP cost less than the discretes that would be needed.
-- -- kensmith@rahul.net forging knowledge
Why is it then whenever anyone talks about this they talk about PSpice as if its the be all/end all of simulators. It's just not. You guys (and gals) should try some real EDA tools, like icfb (Virtuoso Schematic Editor/Analog Environment/Spectre). While I'm not a huge fan of Cadence, they have top notch analog tools, although I prefer Nanosim for big simulations. The schematic editor is more power, flexible and easier to use than Orcad, and the simulator is light years better than PSPICE.
dan
I don't use OrCAD Capture, I use the old original (MicroSim) PSpice Schematics, which is about the best user interface I've ever seen.
My experience with workstation or mainframe-based tools is they are butt slow compared to PSpice running on an AMD chip.
...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 |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
The problem with that statement is, its not an apples to apples comparison. There is no doubt that hardware wise Intel/AMD represent a much bigger bang for the buck in terms of computation power than virtually any other platform. A modern AMD Opteron may not be quite as fast as Sun's high-end stuff, its close, and it beats the crap out of their low end stuff which is still twice the problem.
However, virtually all Eunuchs based CAD packages (at least EE CAD packages) are now available for Linux (x86 architecture). Of those probably about 1/3rd are available in IA64 (Opteron) versions as well and I expect the number to be closer to 80% by the end of 2005.
So basically, there's no reason why you can't run any of the programs I talk about on an AMD chip. In fact, I just got a brand new 16 GB dual Opteron 250 to play with just for Nanosim, and trust me, its fast.
dan
And PSpice costs an order of magnitude less than Spectre...
(or, is it TWO orders of magnitude for all the bells and whistles...)
8-)-- Charlie -- Edmondson Engineering Unique Solutions to Unusual Problems
^^^^^^^^^^^^^^
Nitpick: IA64 == Itanic AMD64 == Opteron/Athlon64
-- Keith
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