Re: [PEDA] AW: SPICE sim question
Rolf, I am not sure of what part of my post you thought was a joke, it was a rather lengthy reply, but I assure you I was not joking about anything. Simulation has to do with the design of robust, reliable, stable circuits at the lowest possible cost. It is not just an RD toy. Anyone who believes they can sit down and design a circuit in one try that lives up to the above goals is kidding themselves. If you ask ten designers to build a heart rate monitor, you will get ten different products. One of them will be better and quite possibly less expensive than the others. Simulation helps zero in and optimize every one of these targets. Gary Packman Rolf Molitor wrote: That has nothing to do with circuit simulation. You were just joking, right ? Rolf Molitor Ing.Buero i2e Remscheid / Germany -Urspr ngliche Nachricht- Von: Georg Beckmann [EMAIL PROTECTED] An: 'Protel EDA Forum' [EMAIL PROTECTED] Gesendet: Samstag, 29. Juni 2002 14:25 Betreff: [PEDA] AW: SPICE sim question Hi Gary, I want to use the simulator for a Monte carlo analyse for the following question. To simplify what I mean is, imagine a bridge circuit with four resistors of 1% tolerance. The circuit is usable, if the bridge - voltage is below a certain limit. How many percent of my circuits are usable so that I can decide what's cheaper, to throw away the bad samples or use of more expensive resistors. Do you know how this is done ? When I looked at the examples, they only calculated the worst case of a circuit, but that's not the question, I want to get the distribution of a parameter. Georg Afshin Salehi wrote: Just out of curiosity, what types of things do you guys run simulations on? Amplifiers, linear and switching power supplies, filters, and just about anything else that will need tweaking on the bench. What drives you to run a simulation on that specific device? Testing for stability, what range of component values (tolerance) will work reliably, gain, rolloff, keeping signal levels away from the rails when designing high gain multi-stage amplifiers, and most important of all, gaining rapid insight into what happens when you go outside the box. Also, nothing catches fire or explodes in a simulator! How accurate is the simulation to a real world bread boarded device? Once you learn how to use simulation I would say about 98% accurate, but there is a giant proviso here, you must have accurate models and you must understand the limitations of the simulation process. I cannot remember the last time a finished product did not behave as the simulation did. The more often you simulate, the better you and your results get. Jon Elson said it takes a day at first then maybe an hour or so each time to remember things, how is that justified to your boss? I am really just curious as to what things people run sims on, how complex those circuits that are simulated are, and if the tests are worth while? I use an old but very capable DOS version ($15,000 when new) of PSPICE. I can hand type an ASCII circuit description page in about a half-hour (three or four op-amps and twenty or thirty passive parts). Another twenty minutes to patch typos and missed connections. After the circuit is running you can do a number of tests in minutes that would take a week on the bench. Whether it is worth the trouble or not all depends on what you're doing. The last thing I did was a strain gauge amplifier (something I never did before). Had the circuit up and running in one afternoon, cost of components about $10 versus a packaged product with similar specs from Omega for $400. Is that worthwhile? My boss thought so. It all depends... Gary Packman Thanks, Afshin * Tracking #: 089C581B73790B40A34A5F9530FFA0A756B58F96 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] AW: SPICE sim question
Georg, I'm not sure I understand your question. What I think you are asking is how to predict the ratio of resistors that will make your bridge stay within certain design parameters versus those that will not based upon a random sample batch of parts. If this is what you're asking my advice is to always purchase components that are within the limits of the design, even if they cost more. Why? Because if you buy 100,000 5% resistors with the expectation that a certain per cent will fall within a 1% tolerance you might end up with 100,000 parts that won't work. Plus, the cost of tolerance testing is generally prohibitive (unless you live in China). Also, cheap components often drift with age. The more expensive high tolerance parts don't drift as badly. If I misunderstood let me know and I'll take another stab at it. Gary Packman Georg Beckmann wrote: Hi Gary, I want to use the simulator for a Monte carlo analyse for the following question. To simplify what I mean is, imagine a bridge circuit with four resistors of 1% tolerance. The circuit is usable, if the bridge - voltage is below a certain limit. How many percent of my circuits are usable so that I can decide what's cheaper, to throw away the bad samples or use of more expensive resistors. Do you know how this is done ? When I looked at the examples, they only calculated the worst case of a circuit, but that's not the question, I want to get the distribution of a parameter. Georg * Tracking #: 8C343605D9618348B4354FE5A2B4188B5609473F * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] AW: SPICE sim question
Also, in practice you'll be very lucky to find a resistor sold as 5% that is within 1% across temperature etc. - they're the ones that are being sold as 1% parts! Regards, Andy Gulliver -Original Message- From: Gary Packman [mailto:[EMAIL PROTECTED]] Sent: 02 July 2002 10:08 To: Protel EDA Forum Subject: Re: [PEDA] AW: SPICE sim question Georg, I'm not sure I understand your question. What I think you are asking is how to predict the ratio of resistors that will make your bridge stay within certain design parameters versus those that will not based upon a random sample batch of parts. If this is what you're asking my advice is to always purchase components that are within the limits of the design, even if they cost more. Why? Because if you buy 100,000 5% resistors with the expectation that a certain per cent will fall within a 1% tolerance you might end up with 100,000 parts that won't work. Plus, the cost of tolerance testing is generally prohibitive (unless you live in China). Also, cheap components often drift with age. The more expensive high tolerance parts don't drift as badly. If I misunderstood let me know and I'll take another stab at it. [cut] * Tracking #: B9849B552B125A41B36E261676C47A7791583C05 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] AW: SPICE sim question
Gary, i did not reply to your post but to Georgs least cost calculator. I myself use simulation tools for several years and would grade them essential. The protel simulation tool should be improved in its user interface (displaying and documentation of the simulation results ...) primarily. No new fancy gimmicks please, keep it simple (no least cost calculator). Rolf Molitor Ing.Buero i2e Remscheid / Germany -Ursprüngliche Nachricht- Von: Gary Packman [EMAIL PROTECTED] An: Protel EDA Forum [EMAIL PROTECTED] Gesendet: Dienstag, 2. Juli 2002 10:50 Betreff: Re: [PEDA] AW: SPICE sim question Rolf, I am not sure of what part of my post you thought was a joke, it was a rather lengthy reply, but I assure you I was not joking about anything. Simulation has to do with the design of robust, reliable, stable circuits at the lowest possible cost. It is not just an RD toy. Anyone who believes they can sit down and design a circuit in one try that lives up to the above goals is kidding themselves. If you ask ten designers to build a heart rate monitor, you will get ten different products. One of them will be better and quite possibly less expensive than the others. Simulation helps zero in and optimize every one of these targets. Gary Packman Rolf Molitor wrote: That has nothing to do with circuit simulation. You were just joking, right ? Rolf Molitor Ing.Buero i2e Remscheid / Germany -Urspr ngliche Nachricht- Von: Georg Beckmann [EMAIL PROTECTED] An: 'Protel EDA Forum' [EMAIL PROTECTED] Gesendet: Samstag, 29. Juni 2002 14:25 Betreff: [PEDA] AW: SPICE sim question Hi Gary, I want to use the simulator for a Monte carlo analyse for the following question. To simplify what I mean is, imagine a bridge circuit with four resistors of 1% tolerance. The circuit is usable, if the bridge - voltage is below a certain limit. How many percent of my circuits are usable so that I can decide what's cheaper, to throw away the bad samples or use of more expensive resistors. Do you know how this is done ? When I looked at the examples, they only calculated the worst case of a circuit, but that's not the question, I want to get the distribution of a parameter. Georg Afshin Salehi wrote: Just out of curiosity, what types of things do you guys run simulations on? Amplifiers, linear and switching power supplies, filters, and just about anything else that will need tweaking on the bench. What drives you to run a simulation on that specific device? Testing for stability, what range of component values (tolerance) will work reliably, gain, rolloff, keeping signal levels away from the rails when designing high gain multi-stage amplifiers, and most important of all, gaining rapid insight into what happens when you go outside the box. Also, nothing catches fire or explodes in a simulator! How accurate is the simulation to a real world bread boarded device? Once you learn how to use simulation I would say about 98% accurate, but there is a giant proviso here, you must have accurate models and you must understand the limitations of the simulation process. I cannot remember the last time a finished product did not behave as the simulation did. The more often you simulate, the better you and your results get. Jon Elson said it takes a day at first then maybe an hour or so each time to remember things, how is that justified to your boss? I am really just curious as to what things people run sims on, how complex those circuits that are simulated are, and if the tests are worth while? I use an old but very capable DOS version ($15,000 when new) of PSPICE. I can hand type an ASCII circuit description page in about a half-hour (three or four op-amps and twenty or thirty passive parts). Another twenty minutes to patch typos and missed connections. After the circuit is running you can do a number of tests in minutes that would take a week on the bench. Whether it is worth the trouble or not all depends on what you're doing. The last thing I did was a strain gauge amplifier (something I never did before). Had the circuit up and running in one afternoon, cost of components about $10 versus a packaged product with similar specs from Omega for $400. Is that worthwhile? My boss thought so. It all depends... Gary Packman Thanks, Afshin * Tracking #: 089C581B73790B40A34A5F9530FFA0A756B58F96 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list
Re: [PEDA] AW: SPICE sim question
no, or not always, or not anymore ;) -first of all, the 1% and 5% being tolerances , are usually specified either at standard temperature (like 25deg C) , or across temperature range. IF the specs are at 25deg C , they don't imply any kind of temperature performance . There will be no relationship whatsoever between a resistor being 1% across temperature and being sold as 1% tolerance. Life is not that easy. There might be different temperature coefficients involved depending on the resistors' technology but that's another story ,they might even be non-linear with temperature . -long ago ,when resistor materials manufacturing costs were the predominant part in the resistor retail price (or so the legend said) , some vendors used to sort their resistors . That way, they were making only 5% parts. They were picking the parts which were within +/-2% and +/-1% from the 5% batch and marked them as 2% and 1% . I recall someone having fun one day , plotting a whole resistors box distribution only to figure out if they were selected as 1% or unselected. The idea was that if they were unselected, we could've selected them for 0.1%, otherwise the middle of the curve was gone and sold as 0.1% . Now, time is a lot more important than materials for resistors , processes are a lot more under control, so I doubt any resistor manufacturer is selecting 1% out of the 5% bin. They might do it for specialty parts , low volume and/or low yield high precision parts but not the 5%. - as a sidenote, the cherry picking procedure makes Monte-Carlo analysis somewhat useless, unless the problem was trivial . That is because the cherry picked parts don't obey any random distribution curve so the combinations Monte-Carlo is calculating in that case don't really exist. Best Regards, Matt Tudor , MSEE http://www.gigahertzelectronics.com - Original Message - From: Andy Gulliver [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Tuesday, July 02, 2002 6:44 AM Subject: Re: [PEDA] AW: SPICE sim question Also, in practice you'll be very lucky to find a resistor sold as 5% that is within 1% across temperature etc. - they're the ones that are being sold as 1% parts! Regards, Andy Gulliver * Tracking #: 1196B5D30963FF4A88A728F6367207E6F00B1513 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] AW: SPICE sim question
That has nothing to do with circuit simulation. You were just joking, right ? Rolf Molitor Ing.Buero i2e Remscheid / Germany -Ursprüngliche Nachricht- Von: Georg Beckmann [EMAIL PROTECTED] An: 'Protel EDA Forum' [EMAIL PROTECTED] Gesendet: Samstag, 29. Juni 2002 14:25 Betreff: [PEDA] AW: SPICE sim question Hi Gary, I want to use the simulator for a Monte carlo analyse for the following question. To simplify what I mean is, imagine a bridge circuit with four resistors of 1% tolerance. The circuit is usable, if the bridge - voltage is below a certain limit. How many percent of my circuits are usable so that I can decide what's cheaper, to throw away the bad samples or use of more expensive resistors. Do you know how this is done ? When I looked at the examples, they only calculated the worst case of a circuit, but that's not the question, I want to get the distribution of a parameter. Georg Afshin Salehi wrote: Just out of curiosity, what types of things do you guys run simulations on? Amplifiers, linear and switching power supplies, filters, and just about anything else that will need tweaking on the bench. What drives you to run a simulation on that specific device? Testing for stability, what range of component values (tolerance) will work reliably, gain, rolloff, keeping signal levels away from the rails when designing high gain multi-stage amplifiers, and most important of all, gaining rapid insight into what happens when you go outside the box. Also, nothing catches fire or explodes in a simulator! How accurate is the simulation to a real world bread boarded device? Once you learn how to use simulation I would say about 98% accurate, but there is a giant proviso here, you must have accurate models and you must understand the limitations of the simulation process. I cannot remember the last time a finished product did not behave as the simulation did. The more often you simulate, the better you and your results get. Jon Elson said it takes a day at first then maybe an hour or so each time to remember things, how is that justified to your boss? I am really just curious as to what things people run sims on, how complex those circuits that are simulated are, and if the tests are worth while? I use an old but very capable DOS version ($15,000 when new) of PSPICE. I can hand type an ASCII circuit description page in about a half-hour (three or four op-amps and twenty or thirty passive parts). Another twenty minutes to patch typos and missed connections. After the circuit is running you can do a number of tests in minutes that would take a week on the bench. Whether it is worth the trouble or not all depends on what you're doing. The last thing I did was a strain gauge amplifier (something I never did before). Had the circuit up and running in one afternoon, cost of components about $10 versus a packaged product with similar specs from Omega for $400. Is that worthwhile? My boss thought so. It all depends... Gary Packman Thanks, Afshin * Tracking #: 089C581B73790B40A34A5F9530FFA0A756B58F96 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
