On Mon, 22 Jan 2024 00:12:36 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:
>On Sun, 21 Jan 2024 19:43:18 -0800, John Larkin <jl@997PotHill.com>
>wrote:
>
>>On Sun, 21 Jan 2024 22:08:08 -0500, Joe Gwinn <joegwinn@comcast.net>
>>wrote:
>>
>>>On Sun, 21 Jan 2024 16:05:07 -0800, John Larkin <jl@997PotHill.com>
>>>wrote:
>>>
>>>>On Sun, 21 Jan 2024 18:16:01 -0500, Phil Hobbs
>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>
>>>>>JL wrote an interesting post in the depths of the "better
>>>>>microelectronics from coal" thread that I thought was worth pulling out
>>>>>on its own.
>>>>>
>>>>>On 2024-01-21 10:12, John Larkin wrote:>
>>>>>
>>>>>"...what IS electronic
>>>>> > design, and what's the best way to do it? <snip>
>>>>> >
>>>>> > Short answer, cobbling. When presented with a problem or an
>>>>> > opportunity to design electronics, the most efficient way to do that
>>>>> > is to grab a piece of paper and immediately sketch a circuit or an
>>>>> > assembly. Sometimes one can do that instantly, without thinking, or
>>>>> > sometimes one can ignore the issue for a few days and then the design
>>>>> > pops up. Sometimes brainstorming and whiteboarding help. Sometimes
>>>>> > fiddling with Spice helps.
>>>>> >
>>>>> > All that literature research and math analysis and simulation and
>>>>> > breadboarding and prototyping are just slow and expensive follow-up
>>>>> > chores for people who don't have 100% confidence in their instincts.
>>>>> > Analysis, sometimes prudent to do, but not design.
>>>>> >
>>>>> > Design is subconsious and instinctive. And it's free! And to some
>>>>> > extent, it can be taught, but seldom is.
>>>>> >
>>>>> > Most of us design things to sell, so do whatever works. We're selling
>>>>> > stuff, not publishing papers.
>>>>> >
>>>>>
>>>>>Hmm. I don't think that I agree in general, because you make it sound
>>>>>as though the process were just intuitively plucking one idea out of
>>>>>somewhere-or-other and cranking it out.
>>>>
>>>>If an idea is new, where else would come from?
>>>>
>>>>>
>>>>>You've often argued in favor of brainstorming, where you get a few smart
>>>>>people in front of a white board and try out ideas to find the best one
>>>>>and flesh it out. We've done that together, very fruitfully.
>>>>>
>>>>>It's possible to do more or less the same thing by oneself, but it
>>>>>requires the ability to tolerate uncertainty for extended periods.
>>>>>(That's a skill well worth developing, which most people are really,
>>>>>really bad at, IME.)
>>>>
>>>>The uncertainty period is probably necessary, to let ones neurons
>>>>prowl the noisy solution space. The period is usually a day or two,
>>>>but can be years.
>>>>
>>>>Some engineers are uncomfortable with uncertainty, and want to lock
>>>>down a design as soon as possible, preferably something sanctioned by
>>>>some authority. I like to stay confused for a while.
>>>>
>>>>>
>>>>>I sometimes need to do a family of designs, rather than just one.
>>>>>Recently I've been working on some very fast, very cheap SPAD preamps,
>>>>>intended to go in the guts of positron-emission scanners.
>>>>>
>>>>>Designs with lots of real-world constraints are often the most fun, and
>>>>>this one's specs include: 300-ps edges with 100-ps timing repeatability
>>>>>from unit to unit; no magnetics allowed; and a BOM cost of $1 or less.
>>>>>(You need a whole lot of channels, and PET and MRI machines are often
>>>>>combined.)
>>>>>
>>>>>I do a fair amount of analysis of circuits of that sort, to figure out
>>>>>what actually limits their performance. It isn't super detailed--in
>>>>>this case, just enough to figure out whether it'll be the base-emitter
>>>>>time constant, the Miller effect, or the SPAD's series resistance that
>>>>>will be the limiting factor.
>>>>
>>>>Certainly quantitative reality should filter the solution space. But
>>>>even that can be mostly intuitive. I was talking about that with C on
>>>>Friday, about how some people have good quantitative intuition and
>>>>some don't. She can look at soup in a round pot and know if it will
>>>>fit into a square plastic container, to about 10%. I can do that.
>>>>Neither of our spouses can.
>>>>
>>>>
>>>>>
>>>>>Miller, I can deal with using circuit hacks. The BE time constant is
>>>>>Rbb' * Cbe, which gets slightly worse at high current, but is mainly a
>>>>>device parameter--to get a big improvement you have to change
>>>>>transistors. The SPAD can be negotiable depending on whose process
>>>>>you're making them on--when each machine needs thousands of them,
>>>>>vendors tend to listen.
>>>>>
>>>>>Eventually, of course, you have to pick one and go with it, but picking
>>>>>a topology usually takes me an iteration or two.
>>>>
>>>>Sometimes a circuit takes me dozens, lots of sheets in the trash can.
>>>>I think it's important to give as many ideas as possible a chance.
>>>>
>>>>See Barrie Gilbert's essay "Where do little circuits come from?"
>>>>
>>>>"Prod and poke" and "doodling" are suggested.
>>>>
>>>
>>>I agree with both of you. What Phil is doing is figuring out where to
>>>focus the brainstorming and fiddling, and the resulting wild
>>>alternatives can easily be assessed. It's at the very least an
>>>orthogonal method.
>>>
>>>My personal experience is that iterations and inspirations require
>>>studying extensively followed by sleeping on it, so the metric isn't a
>>>few days, it's a few nights.
>>
>>Actually, it is a few showers.
>
>So, you're all wet?
That's the idea.
>
>Actually, I also get ideas in the shower, probably because I stopped
>focusing so hard.
I think sleepytime ideas get delivered in a morning shower. I don't
have ideas if I shower later in the day.
>
>I used to keep a waterproof dictation recorder handy, and on my
>bedside table, so I wouldn't lose the ideas, but don't need the
>recorder any more.
Sometimes I have ideas at around 3AM. I scribble them on a pad so I
don't forget.
>
>But the key is to stop trying for a while and think irrelevant things.
>
>Joe Gwinn
>
>
>>>The bit about the necessity of nights was pointed out by J. Hadamard
>>>in his famous book on this issue. The book has become hard to find
>>>and expensive, but has now been reissued:
>>>
>>>.<https://www.amazon.com/Mathematicians-Mind-Jacques-Hadamard/dp/0691029318/ref=sr_1_1>
>>>
>>>Joe Gwinn