The stupidity of slimulations

I once had that skill. Today I always seem to be in a hurry :-(

Once, at a seminar at Kodak (Rochester), I had a heckler...

I feigned that I couldn't understand his issue, brought him up to the whiteboard, where he promptly made a fool of himself. Not quite the same as Dr. Land's method ;-)

The interesting thing is that we became close friends after that. (I won't name him, but if he's still alive... it's been 40+ years, he'll remember :-) ...Jim Thompson

I must be pretty naive then. What materials have >1k relative permeability at 100MHz?

Jeroen --I'm only an egg-- Belleman

Here's the one I used to test possible hires...

...Jim Thompson

An emitter follower is not obtuse, and asking about one is not battering. I don't like trick questions, but any potential electronic designer ought to know how a transistor works.

I ask applicants to show me circuits that they have designed themselves. If they do, we can discuss them and see if they actually remember/understand how they work. I get engineers who can't explain their own (?) designs. I get students who just finished a course, or a class project, who absolutely don't understand what they did.

And I get experienced engineers who tell me that everything they have ever done is covered by NDAs, so they can's show me, even whiteboard, anything that they have done.

Can't hire any of them.

One guy I did hire, we spent the interview afternoon together actually designing a new product. Since I'd paid to fly him and GF to San Francisco, he didn't complain about working unpaid.

Interning is good too, an extended job interview.

They can't have undergone any proper training then. They're phonies who presumably bought degrees over the internet.

Come to think of it, 2 years ago, a young, recently-qualified electrician warned me that "even a few megohms can kill you."

WTF are they teaching in these colleges these days??

Yeah, so now stop jesting. No way is that paper and pencil!

I also commend you on the drawings. Garbled schematics are, imo, a sign of a garbled mind. Its actually rare to get sensible schematics in asic design, because most just don't have a proper understanding of what they are designing.

Regards

Kevin Aylward B.Sc. snipped-for-privacy@kevinaylward.co.uk

Perhaps. One of the precision questions that was passing through my mind was modelling coupling in ferrite-cored transformers.

Laziness on my part. Mainly because I don't use them much.

I have still to make a batch fully paramertised. There is one balun in the genetics lib.

There is a full hysteretic core model for cores in SS. Haven't tried to make a transformer with them. Probably can...

And I wonder - from time to time - whether I should use the same coupling factor for two coils which are actually bifilar wound as I use for the multi-layer secondary I'd get wound on top of it.

Kevin Aylward

As you well know, hierarchical design is just a big stack of small pieces. But a lot of hand work went into the reference generator (aka bandgap), and there are lots of hand calculations involved in optimizing those current mirrors for best headroom while maintaining accuracy.

Thanks! I'm a real stickler for making schematics that flow smoothly and clearly convey function.

Did you play with the hierarchical structure of the PDF's? I make up all my design reviews (and hand-off's to my layout guy) that way.

I like PDF's like that better than PowerPoint. PowerPoint is a real PITA to organize smoothly and quickly. ...Jim Thompson

There are both Voltage Mode and Current Mode controller examples in my SuperSpice

CurrentModeController.sss VoltageModeController.sss

The models themselves will run in any Spice simulator. They take about 5 seconds to run on my Dell. It used to be that you would need all sort of fancy stuff to realistically simulate SMPS, but not so any more. 50 GFOPs is a no brainer today.

I "designed" them by drawing a schematic, and using the create subckt from schematic feature.

Kevin Aylward

I create most of my subcircuits that way... and it's also a nice way to document how you derived the model. ...Jim Thompson

Note that any XSPice based simulator, i.e. most of them apart from PSpice and LTSpice, has an inherent model that has current sensing power supply leads with output resistance.

e.g.

.SUBCKT AMP_XN 0_in 1_pv 2_nv 3_out ao=1 ro=0.1 i_max=750m

.param smooth=0.01 a1 in pv nv out amp_a .model amp_a ilimit(in_offset=0.0 gain={ao} r_out_source={ro}

• r_out_sink={ro} i_limit_source={i_max}
• i_limit_sink={i_max} v_pwr_range=0.01
• i_source_range={i_max*smooth} i_sink_range={i_max*smooth}
• r_out_domain=1e-3) .ENDS

This can be added to the inbuilt slew limiter + RC poles to make quite a decent, realistic op-amp simulating fast.

Kevin Aylward

On a sunny day (Sun, 23 Mar 2014 10:31:41 -0000) it happened "Kevin Aylward" wrote in :

Misconception really. QM is coloured noise with brick walls. Somethings might be possible in almost every location, most can't and have a zero probability of being in many places. That includes Heather Locklear being in my bedroom.

Kevin Aylward

That brings up a point in Quantum Mechanics. The state vector is NOT an Add or Or sign as in "its in two places of once" nonsense. Its a logical

Kevin Aylward B.Sc.

There have been many well-substantated incidents of aports over the years, Kev. The interesting bit, the clue if you like, is that these curious events become very much less common as the size of the object in question increases.

The latter actually DID happen while talking with a National Semiconductor Designer [un-named designer]. His bull-headedness at thinking he was correct while not entering into any kind of discussion to clarify was the most amazing experience in analog design I've ever gone through.

Yes. I do do that as first go. "Tell me how you would design an amplifier" ? "What are the trade offs" etc.

However, overwhelmingly, I find that most typical 10 year alleged analog engineers, know essentially, nothing. Its just the way it is.

It doesn't help either when standard teaching material is fundamentally flawed, and understood in that erroneous way.

Every day I wonder how my iPhone actually works. Some must be able to do the job, because it does, but there are very few.

I am almost getting as grouchy as Mr. Thompson in my decade away from old age...

Kevin Aylward

On a sunny day (Sun, 23 Mar 2014 18:39:01 -0000) it happened "Kevin Aylward" wrote in :

You could perhaps lower the tunnel barrier by calling here?

In my "spare" time ;-) I've been twiddling all the physical aspects of an OpAmp output stage, but haven't had time recently to pursue it, but my basic OpAmp model is here...

...Jim Thompson

Welcome to the club ;-)

My "run-in" was with an NXP PhD.

I just turned 74, and have never felt better... cutting back just one glass a wine a night has dropped me nearly 20 pounds :-) ...Jim Thompson