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Old 29th July 2003, 01:01 AM   #11
The one and only
 
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Join Date: Mar 2001
A cursory inspection does not show a conceptual flaw.

Two points:

1) A lot of people send me schematics, many of them quite
complex, and want to know how they'll work. I don't mind this,
but I do have limited time, and I don't want to publicly embarrass
myself, so sometimes it takes me a long time to figure them out.
Sometimes I never do.

2) I keep saying: Don't treat simulations with the same
reverence you might give the Ten Commandments. I have a
couple of books on my shelf devoted to the flaws of Spice, and
I assume there must be some. Just because Spice says
something will/won't work doesn't mean it's chiseled in stone.

This seems to be particularly true of X circuits because of the
easy potential for the "hall of mirrors" effect.

In the end, you must build the circuit (That's why this is DIY,
not SIY)
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Old 29th July 2003, 11:24 AM   #12
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Hi,

Me and my simulator have a great relationship...

I don't push her with many current sources/voltage sources, complex and long feedback loops (aka Hall of Mirrors), nor do I expect her to caculate gains in biljoens, voltages and current in the 10e6 range or more than 1000 point per sine cycle ... these things make her sick..

If I commit myself to her rules then she loves giving me the hot stuff she's so good at... I love her!

Regards,
Thijs
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Old 29th July 2003, 11:41 AM   #13
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Hi Grataku,

Only the look of your schematic make my dear simulator sick .. I think you need to be a little more frendly ... toooooooo may voltage sources and current sources and stuff... for my simple mind at least...

So I have some suggestion, those are just that.. suggestion .. I'm not saying I am an expert, but my schematic does simulate and it simulates with very good results..

-I see no bias voltage for the input transistors and no current stabilisation resistor either... I really think those are needed..
-skip I1, I2, I3, I4 and use resistors..
-Skip the output power stage and see if you can get it to work as a preamp first, then add the output stage..
-use 100R / 1000R input/feedback resistors at first..
-skip the gate-snoopers at first

My circuit only uses two Powersupply voltage sources and 1 signal generator voltage source (split with low R's to give balanced operation) .. the rest is simple passive... this really should work...


Goodluck,
Thijs
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Old 29th July 2003, 02:44 PM   #14
uli is offline uli  Austria
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Talking quote

Quote:
Originally posted by Nelson Pass
In the end, you must build the circuit (That's why this is DIY,
not SIY)

I quote this "statement of the year!"

lofl





Uli
__________________

'Jazz is not dead, it just smells funny' F.Zappa
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Old 29th July 2003, 05:22 PM   #15
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Default Spice and price

If any of you planning on simulating a circuit this complicated on a Spice demo program forget it. They are node limited to get you to buy the real thing. Even sometime a simple is a pretty basic amplifier circuit can cause the simulation not to run and the program will not tell you why.

Mr. Pass is absolutely right about building stuff instead simulating it. Despite novices opposite opinion. Spice will not teach you to design even bad amplifiers, much less good ones. The vast majority the circuits that I see the new guys post and be convinced would be a good circuit are not. When I first ran Spice in school I saw guys submit two programs at once, one increasing a parameter, and the other decreasing the same parameter; to see what the circuit would do! I am afraid that is actually computer aided guessing not CAD (computer aided design) Many in the engineering community feel the reliance on simulation tools without the feel and understanding of the fundamentals. Guys that do not have a feel for what a single transistor does from studying the data sheet and building and measuring simple circuits now trust simulators even to design 500,000 transistor ASIC with only computer design tools and without a clue as to the problems that can cause the actual physical circuit to have problems. Often problems that don't show up until after months of testing in the real world. Spice is only useful after you have built stuff and understand how it works and doesn't work in the real world. It is impractical and even impossible to build very complicated circuits without some simplified math and Spice models. An amplifier is not one of those circuits. I use it very carefully and know how simplified the models are. None of the parasitic like wiring inductance are usually modeled and there're a hundred this in a physical circuit that are not on the schematic of in the Spice model. Valuable learning time at the lab bench is being wasted at the simulator. I have scene transistor models posted hear from supposedly reputable source that were not even close, because people did not do a reality check of comparing the model parameters to the data sheet.
I am also alarmed because I never see the circuits that Nelson and Erno Borbely have built measured and documented, modeled with Spice, to see how close it came to the real thing. It can be a powerful tool used in the right context and with enough experience. But only with real measurements to confirm the model is close to a real functioning physical circuit to be useful for anything. Using it to skip the steps that will give you a feel for how a circuit really works and to keep from having from having to make measurements, will not help you become a designer but will absolutely assure that you won't. Take it from 20 years of experience, it is a supplement to the design process and not the design process in it's self. Do not forget that the A in CAD is for AIDED. I can't even begin to count the number of times I have seen people talk about distortion measurements for op amp models. An op amp model is not even built of idealized transistor models but is mostly linear controlled source elements that don't come close to describing even an idea model of a transistor circuit much less a real circuit. And you are going the make distotion predictions from that? I fall down on the floor when I see stuff like this.
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Old 29th July 2003, 06:23 PM   #16
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Location: The Netherlands
Well DirtyHarry,

I trust your right and your remarks are noted.

Quote:
I am also alarmed because I never see the circuits that Nelson and Erno Borbely have built measured and documented, modeled with Spice, to see how close it came to the real thing.
If I remember correctly you made this remark also about a year ago, maybe even two years ago.. I also remember that at the time I absolutely agree with the remark. The BOZ and BOSOZ articles should be very usefull for evaluating SPICE results. I'll give it a try........

I must admit that I spent too much time behind the simulator, and built to little. Somehow the SPICE simulator is more addictive than Red Alert, Quake and Unreal together...

But back to the main topic .... the simulatyor didn't work correctly on the Fig. 4 circuit of the Patent. I've had no problems with the Fig. 3 circuit. My simulator is ha#$%cked , no demo, but is the real thing.. (I'm not proud of that) ... maybe that helps. I also try to stay away from infinite low and infinite high nodes like voltage sources and current sources.. I think that helps too ..

One problem I always have with my simulator is that I have always infinite good match transistiors ... So distortion measurements are not valid if only because of that.... Maybe especially in differential circuits like SOZ, BOSOZ, and various SuperSymm circuits..


Regards,
Thijs
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Old 29th July 2003, 08:30 PM   #17
grataku is offline grataku  United States
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Nelson,
what I am doing here is nothing too serious, as I said, I simulated all the circuits in the susy patent as they appear on the patent and they all worked except the last one, that made me wonder.

Fred,
I used Aplac to simulate RF probes and the result is off the chart compared to the real thing.
However, when one inputs the correct measured parameter that accnt for the parasitic inductance and capacitance the results are remarkably good.

That's RF and this is audio freq.

Anyway you can rest assured: nothing that comes out of my playing with simulator will yield a commercial audio product.
I do other things in my real job.
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Old 29th July 2003, 11:44 PM   #18
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This website gives an example or 2 how to improve SPICE reliability.. a bit off topic but a nice website I think..

http://www.beigebag.com/case_headamp1.htm

Regards,
Thijs
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Old 30th July 2003, 01:26 AM   #19
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Quote:
Originally posted by Fred Dieckmann

Many in the engineering community feel the reliance on simulation tools without the feel and understanding of the fundamentals.

The same thing happens in our professional field. I call it a "black box." Many engineers use the black box without understanding how it is formed, what principles are applied, what are assumed, etc. They just believe in its results of often eccentric conclusions, and their opinions are strong in general.

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Old 30th July 2003, 07:25 AM   #20
andy_c is offline andy_c  United States
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Quote:
Originally posted by tschrama
The error message says: 'line too lone ... no such vector.....' etc ..
Hi Thijs,

Sounds like a Circuitmaker error message? I saw this "no such vector" error message last weekend. The name of the "vector" it gave, something like d11 or d_11 or something like that, turned out to be associated with the component named D11 in my schematic. I deleted it, then added a new one back in. Then I noticed the new one had a different reference designator (it was something like D6 now, instead of D11). After I made this change, the circuit simulated okay. I think Circuitmaker has some kind of element renumbering bug that causes the schematic to get out of sync with the netlist sent to the simulator. At least, that's my guess. So if you see the "no such vector" and the name of the vector looks like the name of a component, try deleting the component and adding it back in. It worked for me.

I haven't tried simulating any of Nelson's circuits though.
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