Thinking process involved when designing analog electronic circuits

That's interesting, I've never used Spice, and haven't had any problems. As someone else mentioned, one needs to get the Block Diagram specified, and from there, each block is a familiar doable. Why would you NEED Spice? Regards Ken

the

=A0waste time

Sounds like your resume would go straight into his trashcan :-)

In article , To-Email- snipped-for-privacy@My-Web-Site.com says...>

They'd better be or *nothing* works. Since you rely on cross-chip tracking the models have to be quite good.

Take a look at the crap that board designers tend to get stuck with. :-(

Depends on the definition of "absolute tolerances" is. One of the "absolute tollerances" you depend on is tracking. ;-) Board designers don't have such luxuries. I needed a current "source" for what I'm doing now. The double-darlington we've been using is dead, so had to find a substitute. Fortunately I didn't need much current (a couple of mA) so didn't really need the darlington. I settled for a part with two (adjacent) dice from the same wafer ($6). Spice doesn't help with the cost either. ;-)

simple one

Hardly any learning there. ;-)

Same here, except that almost half of my engineering career was done without benefit of a simulator.

My yield then was every bit as good as it is now.

Simulators have simply bought me the ability to design devices that run faster than any breadboard would have allowed. AND a much higher transistor count... most of my early stuff rarely exceeded 300-400 transistors.

...Jim Thompson

Worse than that, the best designers I know would snicker at the beaucracy. Component level sims are good if you need to R&D a new circuit, but who wants to do that? Anyway the sim still needs judgement. The big picture needs to account for the information movement which can be sourced from a driver source, fiber optic, phone line, duplex satelite and on and on. (I'm pro sim BTW)

What's the most complicated system you guys have had to design - troubleshoot?

Generally the ones that give me problems are ones with multiple feedback loops. Regards Ken

"Cross chip tracking"? Ain't no such animal. Only local (accurate" matching. Special efforts are necessary to send references around the chip.

I was talking of device libraries. Board designers generally don't do circuit design.

"Absolute tolerance" means just that... resistor absolute value tolerances may be as high as 30%

"Tracking", in terms of temperature, yes. More important is "ratio" matching, which can be made to 1% (or less with some special effort).

Or you can be clever, and make a 10-bit ADC, from 3% resistors ;-)

Or more cleverness in your design skills ?:-)

All my parts are "free".

Occasionally part of my job includes teaching the client... not that much sticks... it takes _years_ to develop your own bag of tricks.

...Jim Thompson

In article , To-Email- snipped-for-privacy@My-Web-Site.com says...>

You aren't *that* old. I was using a simulator for ASICs (before the term was coined) in the '70s.

Measured by the transistor?

...just a little bit of productivity. ;-)

Sure there is. Tracking may be a function of distance and orientation, but there certainly is tracking across a chip. There is tracking across wafer, as well, though obviously not as strong. Models can (and do) incorporate any or all such tracking. It's pretty hard to do manually though.

Tell Larkin that. ;-)

Or perhaps 2-5% for board designers. Tracking can still be fun.

Ratio matching is part of tracking. There are still tolerance terms.

...as long as you have .1% tracking somewhere.

Perhaps, though money matters to the owner. I try to keep in mind that I'm spending his money.

In my previous life the cost per transistor was even lower than yours. When there are a few million on a chip... ;-) In this life one has to justify (if only to one's self) the cost of each package.

Sure. I've never been afraid of teaching. However, teaching learning. Besides, every time I taught someone how to do my job I got a better one.\\

But you worked for "mother" in Burlington ?:-)

I didn't have access to a VAX until around 1980, running Berkeley Spice (IIRC) 2g6, fortunately written in Fortran, allowing me to patch the bad representation of the B-E capacitance.

No. Measured by conformance to spec.

Yep.

...Jim Thompson

I did my first control system simulation - the throttle control system of the LASH ships, including hull dynamics - on an HP9100 programmable calculator, ca 1969. Shortly later I bought a PDP-8 and programmed sims in FOCAL. Computers are great for evaluating nonlinear closed-loop systems, where theory doesn't apply for any number of reasons.

I wrote code to do this, but I suppose it could have been done with Spice too.

John

I had forgotten those programmable calculators. I had a TI (84?) that could read a magnetic strip. At that time (~1970+) I used it for locating pole-zeros for active filters.

...Jim Thompson

Actually, Poughkeepsie, then. I didn't move to BTV until '93, when the bipolar mainframes crashed.

Perhaps I should have added the ';-)', but thought I'd done enough.

that

Lord, those were the years. I was using a Model 33(?) TTY machine and GE timeshare to do some microstrip and quarter-wave pin diode attenuator calculations - the "modem" was a box that you put a telephone handset into for acoustic input/output coupling. As I vaguely recall, we either used Fortran or the original Dartmouth Basic as the language. It was either that or go up to the computer department ("IT" hadn't been invented yet) with a stack of punch cards and do the debugging of each individual instruction by hand...eccchh.

I also had a machine in my office, about the size of a desk phone, that used a plain old Rat Shack cassette tape as the storage device. WOrked fine if I had half an hour to load and execute each program.

Jim

...

Oh ... a 'lectric eraser! My dad was a civil engineer, before computers. Drafting table, ink on vellum, etc & a 'lectric eraser. What I don't see in the pic is the brush - anybody who's serious about erasing has a brush. Yours must be out of sight.

, Bob

Electronic principles by Albert Malvino is usually well regarded.

It's on a brass hook on the bookshelf, right in reach.

John

Real designers don't need erasers ;-)

...Jim Thompson

And for a good reason! But I guess the interconnection in an ASIC are modelled as well.

I bet there is a lot of nifty stuff in your libraries.

Tolerances always have some effect on your circuit. It just depends on how much of that effect you tolerate. One of my electronics teachers once said: "electronics is about cancelling errors and tolerances".