Re: 6 bit binary attenuator. - 6 bit attenuator.pdf

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>>>> >>>>>> >>>>>>>> >>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>> Lots of online calculators are available. >>>>>>>>> >>>>>>>>>I use this. I'm not sure how good or otherwise it looks in Excel, it

was made using Sun Microsystems' Star Office, and exported as XLS. I hope the bitmap appears in the right place to overlay the value fields, I don't have Excel, to try it.

>>>>>>>> >>>>>>>>>It produces theoretically image-matched attenuators for any combination

of input and output resistances and any value of attenuation. Unrealizable combinations just result in negative values.

>>>>>>>> >>>>>>>>>Derived from Radiotron Designer's Handbook, Chapter 4, "Theory of

Networks", Sect. 8(v) "Image impedances and image transfer constant of four-terminal networks". Equations 17a thru 17f apply. There's a neat trick to get rid of the hyperbolic functions.

>>>>>>>> >>>>>>>>>I wrote it about 30 years ago, as an HP41CV calculator app, and

subsequently made a spreadsheet out of it.

>>>>>>>> >>>>>>>>>See attached file. >>>>>>>> >>>>>>>> >>>>>>>>Ooh, very nice. Thanks. JF can use that to fix up his design. >>>>>>> >>>>>>>--- >>>>>>>Actually, I'm close to fixing the math errors in my design, which seem >>>>>>>to have come from a trusted source, and which I'll post when I'm done. >>>>>> >>>>>>You must mean formerly trusted source. >>>>> >>>>>--- >>>>>Nope, they're still trusted, by-and-large, because of previous >>>>>flawless performance. >>>>> >>>>>If I get a bad hit again, though, they'll bear a little closer >>>>>watching. >>>>> >>>>>Kinda like where you are now, where truth bows to face and I must >>>>>therefore consider you less than trustworthy. >>>> >>>>All you have to do is look at the values of the first tee, which I >>>>did, and it's obvious that it won't attenuate 32 dB. I don't trust >>>>anything without giving it a sanity check. >>> >>>--- >>>PKB, since didn't your recent little resistor fiasco come about >>>because of excessive trust and inadequate sanity check? >> >>Resistor fiasco? You mean the 0.05% thinfilms? Not the same thing at >>all. > >--- >ISTR that you trusted your vendor enough to supply you with the right >stuff that you didn't do the sanity check of an incoming inspection >and, consequently, you got bit on the ass for your fox paws.

We have 5325 different parts in stock, 2.08 million pieces, so things like that happen once in a while. We can't possibly incoming inspect every part we buy. Imagine setting up test jigs for opamps, microprocessors, FPGAs, bare PC boards, transformers, sheet matal, all that. I have done flight hardware for spacecraft, where every single part is tested and certified and traceable, and that's absurdly expensive.

We do have procedures for picking up on parts problems in production test, or from field returns, and investigating any patterns. That's how we caught the resistor problem. In fact, it was a BIST reutine run on an RTD acquisition section that found it, namely a circuit that uses two resistors and checks them against one another.

>Which airplanes do you have stuff flying on, or you supply GSE for, >anyway?

We don't have much actually flying. Some on the U2, some heads-up display stuff on some AH130s. Most of our stuff is used in engine and FADEC development and test cells (United Airlines uses our gear to test APUs). We do some ground test stuff for B52 radars. That's a good mix, aerospace but no mil or FAA certifications, which are a lot of work.

--- > >>>>Trust is no substitute for checking. As systems get more complex, the >>>>margin for risk goes down. >>> >>>Spare me the pontification of platitudes, blowhard. >> >>Check your math, doofus. > >--- >All in good time, and at my leisure.

Did you use one of those online calculators? A lot of them are plain wrong. I also suspect a lot of people are copying one anothers' javascript, because I see the same wrong calculators in multiple places.

A lot of microstrip-type calculators are wrong. Try a really wide trace; the bad ones will report a negative impedance.

We could start a list of bad online calculators.

John

Reply to
John Larkin
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John Larkin Inscribed thus:

Now that could be a good idea ! But it shouldn't prevent checking and confirming a result. :-)

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Best Regards:
                          Baron.
Reply to
Baron

We could start a list of bad online circuit "designs" by Larkin ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Very second-childhoodish of you Jim.

Reply to
John S

Heck, he's up to childhood 2.5.

John

Reply to
John Larkin

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