On 11 Mar 2020 06:28:32 -0700, Winfield Hill <winfieldhill@yahoo.com> wrote:>Bill Sloman wrote... >> >> There are other ways of predicting what a circuit will do, >> and you can - in principle - create you own Spice models of >> parts which better reflect what they do in the circumstances >> in which you wish to use them. > > I like to make small SPICE models of parts, derived from > analytical expressions of a few critical things that're > going on in the aspect of the circuit I'm evaluating. > > For example, consider an op-amp driving a power MOSFET to > create a controlled current source. The FET's high gate > capacitance, along with the bootstrapped source resistor, > creates a confusing control loop. My RIS-796, a 250-amp > LED pulser project, uses this. If you want, sets of files: > >https://www.dropbox.com/sh/tcmiahzzughadfk/AABtgFDy01cuTDWDRjujP6jva?dl=1 > > In AoE x-Chapter 4x.26, we struggled and derived a set of > analytical equations for this circuit. See article here. > >https://www.dropbox.com/s/o4g4mhzl70rsi9t/4x.26_MOSFET_CS_nodal-analysis_final.pdf? >dl=1 > > The circuit basis for the equations uses the MOSFET's gm, > equation id = gm (vg-vs), and its gate capacitance, Ciss. > The equations are hairy. But we also suggest you can make > a simple SPICE circuit with the op-amp, the FET's id and > Ciss, plus additional Rs and Cs, to evaluate the circuit. > > Such a scheme may only works well over a limited range of > conditions, e.g., using the value for gm at the FET's 250A > current, means that the reduced-current startup won't be > accurately modeled. But it's still quick and useful. And > you can repeat the SPICE run, with lower values of gm, to > get an idea of what's happening during the pulse startup.Nearly all interesting systems are nonlinear, and analytic equations are hard or impossible for nonlinear systems. So the math becomes guidance, suggestions or starting points for simulation or experiment. -- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
"Mike Engelhardt has parted ways with Analog Devices"
Started by ●March 4, 2020
Reply by ●March 11, 20202020-03-11
Reply by ●March 11, 20202020-03-11
jlarkin@highlandsniptechnology.com wrote...> >On 11 Mar 2020 06:28:32 -0700, Winfield Hill <winfieldhill@yahoo.com> >wrote: > >>Bill Sloman wrote... >>> >>> There are other ways of predicting what a circuit will do, >>> and you can - in principle - create you own Spice models of >>> parts which better reflect what they do in the circumstances >>> in which you wish to use them. >> >> I like to make small SPICE models of parts, derived from >> analytical expressions of a few critical things that're >> going on in the aspect of the circuit I'm evaluating. >> >> For example, consider an op-amp driving a power MOSFET to >> create a controlled current source. The FET's high gate >> capacitance, along with the bootstrapped source resistor, >> creates a confusing control loop. My RIS-796, a 250-amp >> LED pulser project, uses this. If you want, sets of files: >> >>https://www.dropbox.com/sh/tcmiahzzughadfk/AABtgFDy01cuTDWDRjujP6jva?dl=1 >> >> In AoE x-Chapter 4x.26, we struggled and derived a set of >> analytical equations for this circuit. See article here. >> >>https://www.dropbox.com/s/o4g4mhzl70rsi9t/4x.26_MOSFET_CS_nodal-analysis_final.pdf?>>dl=1 >> >> The circuit basis for the equations uses the MOSFET's gm, >> equation id = gm (vg-vs), and its gate capacitance, Ciss. >> The equations are hairy. But we also suggest you can make >> a simple SPICE circuit with the op-amp, the FET's id and >> Ciss, plus additional Rs and Cs, to evaluate the circuit. >> >> Such a scheme may only works well over a limited range of >> conditions, e.g., using the value for gm at the FET's 250A >> current, means that the reduced-current startup won't be >> accurately modeled. But it's still quick and useful. And >> you can repeat the SPICE run, with lower values of gm, to >> get an idea of what's happening during the pulse startup. > > Nearly all interesting systems are nonlinear, and analytic > equations are hard or impossible for nonlinear systems. > > So the math becomes guidance, suggestions or starting > points for simulation or experiment.In the case of an op-amp driving a FET, at low currents the circuit will be slower, OK, but the pulse quickly moves past that to the high current. So making sure the loop is stable at high currents, and checking response is most of the game. -- Thanks, - Win
Reply by ●March 11, 20202020-03-11
Bill Sloman <bill.sloman@ieee.org> wrote in news:0092411a-a71f-4805-84cf-9c8b1a2bf5bd@googlegroups.com:> On Wednesday, March 11, 2020 at 7:10:45 PM UTC+11, > DecadentLinux...@decadence.org wrote: >> buecherk@gmail.com wrote in >> news:22bc8f63-d755-4b3d-830f-6eeadee6b608@googlegroups.com: >> >> > >> >> Engineering involves thinking about what you are doing. If you >> >> rely only on intuition you are an artist, not an engineer. >> > >> > No. No good efficient engineering without intuition. >> > >> > There are 37 possible solutions to my problem. I could try them >> > one by one and finish in 2027. I could simulate for hours, do >> > analysis and calculations, to determine where to start. >> > >> > Good intuition and experience 'might' make me choose the right >> > one at the startoff. And then, combine that with good >> > engineering and simulation and soldering and .... >> >> Yes. Many inventions are not new, but are variations on >> previous >> themes. > > Less than obvious variations - "not obvious to those skilled in > the art". > >> Everything is one step at a time, but even though we know so >> very >> well how to walk, we still do not venture forth blindfolded. > > If you don't think about what you think you know, and haven't got > a clear idea of why you think that, you are working in the dark. >Good job of being too stupid to know that what I said was that it takes "A bit of both". <https://youtu.be/TRvlKEvoQEI?t=16>
Reply by ●March 11, 20202020-03-11
On Tuesday, March 10, 2020 at 7:30:24 PM UTC-4, Phil Allison wrote:> John Larkin wrote: > > --------------------- > > > >Bill Sloman is Totally Weird wrote: > > > > > >--------------------------------- > > >> > > >> > > > >> > "Intuition is the most important part of engineering." > > >> > > > >> > That's great. > > >> > > >> It's actually insane, > > > > > > > > >** What an absurd claim. > > > > > >Makes it very clear that Bill has none so has no clue what it is - apart from reading a dictionary. > > > > > > One of Jim Williams' books has a great chapter by Barrie Gilbert, > > "Where do little circuits come from?" > > > > I've known lots of engineers who just tweaked circuits they found on > > data sheets or on eval boards. One guy I know has a nice little > > business basically repackaging eval boards. > > > > > > > >Good engineers have "insight" = a deep understanding of how stuff works. > > > > > >This leaves all the software guys gasping. > > > > > >Insight informs one's "intuition" - so your assessment of what might be possible with what is currently available is very good. > > > > > > > > > > > >> but if intuition is all you've got, you might agree. > > > > > > > > >** And if you have none you are stuffed.Yep. Math is for verifying an idea after the fact. Or sometimes predicting that a better idea is possible. But without the idea first, there's nothing to do the math on.> > Most people get along fine without ever having original ideas. Society > > only needs a small minority of creative lunatics. > > > > Spice hugely improves creating and testing wild ideas. > > > > I'm just now iterating a complex design using a soldering iron. It's a > > huge pain. The parts I'm battling don't Spice well. > > > > > > ** JL leaves you wondering if he is in agreement - or not.He was agreeing and elaborating, adding a current example.> Guess he just likes to "have an edge" as Mr Eastwood remarked.Cheers, James Arthur
Reply by ●March 11, 20202020-03-11
On Tuesday, March 10, 2020 at 6:49:50 PM UTC-4, George Herold wrote:> On Monday, March 9, 2020 at 10:56:08 AM UTC-4, jla...@highlandsniptechnology.com wrote: > > On Mon, 9 Mar 2020 04:14:07 -0700 (PDT), bulegoge@columbus.rr.com > > wrote: > > > > >Przemek Klosowski.... thank you for pointing to that interview on YouTube. I really liked the guys view on what the ltspice program is for which is so that the engineer can get better intuition as to how his circuits work. It is a piece of verification but should not be used is the sole purpose of verifying. I guess I like it because it resonated with my viewpoints about use of such a program > > > > Being an IC guy, he did miss that a little as regards PC boards. I > > often use LT Spice as the only process before I go to a PC board, but > > then PC boards can be modified a lot easier than linear ICs, and parts > > are mostly temperature stable as purchased. > > > > And I design using LT Spice. Once one has some intuition, one can just > > throw parts around in the sim and see what happens. That works > > surprisingly well. I have several circuits in production that I don't > > really understand. > > > > I do much less math than I used to do. I guess rough values and tweak > > in LT Spice. Voltage dividers, filters, oscillators this week. So it's > > a calculator, too. > > > > It also draws presentable diagrams to include in emails and manuals. > > It's a drawing program. > > > > I've had his same thought before: Romans built waterworks, people > > built bridges and cathedrals and cannons and sailing ships, before > > Newton invented calculus. Most science explained what people had > > already built. > Sure, You'll also agree that generations of wisdom went into > mixing the right mortars, smelting iron/steel > and breaking masts with sails*.And to John's point, much of that steel came to us by Bessemer's fiddling not suggested to him by any equation unavailable to everyone else, but by sheer dogged empirical determination, then additions and refinements from later minds. And why did Bessemer do it? Wiki says he was inspired by a conversation with Napoleon III to solve the high price of artillery. I.e., the need was to facilitate war. Bessemer's motivation? Possibly profit. He made some astute business maneuvers suggesting so. And the innovation and the cheap steel that resulted certainly wouldn't have happened in a socialist country, without that profit motive. (And think of the loss to humanity, think of the world today without cheap steel...) But personally, like some of us, I think Bessemer did it because he was having a blast.> I totally agree about intelligent fiddling. (intuition) > which you only get by fiddling with stuff. > > I should do more ltspice. I mostly fiddle with solder. > > George H. > Oh Przemek, thanks for the video.Cheers, James Arthur
Reply by ●March 11, 20202020-03-11
On Wed, 11 Mar 2020 12:00:07 -0700 (PDT), dagmargoodboat@yahoo.com wrote:>On Tuesday, March 10, 2020 at 7:30:24 PM UTC-4, Phil Allison wrote: >> John Larkin wrote: >> >> --------------------- >> >> > >Bill Sloman is Totally Weird wrote: >> > > >> > >--------------------------------- >> > >> >> > >> > >> > >> > "Intuition is the most important part of engineering." >> > >> > >> > >> > That's great. >> > >> >> > >> It's actually insane, >> > > >> > > >> > >** What an absurd claim. >> > > >> > >Makes it very clear that Bill has none so has no clue what it is - apart from reading a dictionary. >> > >> > >> > One of Jim Williams' books has a great chapter by Barrie Gilbert, >> > "Where do little circuits come from?" >> > >> > I've known lots of engineers who just tweaked circuits they found on >> > data sheets or on eval boards. One guy I know has a nice little >> > business basically repackaging eval boards. >> > >> > > >> > >Good engineers have "insight" = a deep understanding of how stuff works. >> > > >> > >This leaves all the software guys gasping. >> > > >> > >Insight informs one's "intuition" - so your assessment of what might be possible with what is currently available is very good. >> > > >> > > >> > > >> > >> but if intuition is all you've got, you might agree. >> > > >> > > >> > >** And if you have none you are stuffed. > >Yep. Math is for verifying an idea after the fact. Or sometimes >predicting that a better idea is possible. But without the idea >first, there's nothing to do the math on. > >> > Most people get along fine without ever having original ideas. Society >> > only needs a small minority of creative lunatics. >> > >> > Spice hugely improves creating and testing wild ideas. >> > >> > I'm just now iterating a complex design using a soldering iron. It's a >> > huge pain. The parts I'm battling don't Spice well. >> > >> > >> >> ** JL leaves you wondering if he is in agreement - or not. > >He was agreeing and elaborating, adding a current example. > >> Guess he just likes to "have an edge" as Mr Eastwood remarked.I am under no obligation to make sense, other than having my circuits work. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 11, 20202020-03-11
On Wed, 11 Mar 2020 00:45:47 -0700 (PDT), buecherk@gmail.com wrote:> >> Engineering involves thinking about what you are doing. If you rely only on intuition you are an artist, not an engineer. > >No. No good efficient engineering without intuition. > >There are 37 possible solutions to my problem. I could try them one by one and finish in 2027. I could simulate for hours, do analysis and calculations, to determine where to start.There might be 1e7 solutions to your problem. You can't simulate them all. You can sleep on it and let your brain evaluate the 1e7 solutions and pick a few good ones to simulate.> >Good intuition and experience 'might' make me choose the right one at the startoff. >And then, combine that with good engineering and simulation and soldering and ....But don't commit too soon. It's best to stay confused for a few days. It's also very helpful to talk to someone else about a circuit concept. I just did that, and the results were good, if hard to draw.> >Klaus-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 11, 20202020-03-11
John Larkin wrote: ------------------>> > >> ** JL leaves you wondering if he is in agreement - or not. > > > >He was agreeing and elaborating, adding a current example. > > > >> Guess he just likes to "have an edge" as Mr Eastwood remarked. > > I am under no obligation to make sense,** ROTFL - John, you have certainly succeeded in that direction. Wot a bullshitting ass. ..... Phil
Reply by ●March 11, 20202020-03-11
On Wed, 11 Mar 2020 14:44:34 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:>John Larkin wrote: > >------------------ > >>> >> >> ** JL leaves you wondering if he is in agreement - or not. >> > >> >He was agreeing and elaborating, adding a current example. >> > >> >> Guess he just likes to "have an edge" as Mr Eastwood remarked. >> >> I am under no obligation to make sense, > > > >** ROTFL - John, you have certainly succeeded in that direction.Yes. The circuits almost always work first try. Read this: https://www.amazon.com/What-Care-Other-People-Think/dp/0393355640/ref=sr_1_2?keywords=book+feinman+people+think&qid=1583964038&sr=8-2 -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 11, 20202020-03-11
John Larkin is Nuts wrote: -----------------> > > >>> > >> >> ** JL leaves you wondering if he is in agreement - or not. > >> > > >> >He was agreeing and elaborating, adding a current example. > >> > > >> >> Guess he just likes to "have an edge" as Mr Eastwood remarked. > >> > >> I am under no obligation to make sense, > > > > > > > >** ROTFL - John, you have certainly succeeded in that direction. > > Yes. The circuits almost always work first try. >** He did it again !!! Wot a hoot.
