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Re: Op-amp mystery

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On 9/11/2024 3:59 PM, Lasse Langwadt wrote:
> until all the inputs are low, then it only works until the bypass cap is 
> discharged ;)

Never a problem when your Vcc looks like a 2 ohm load and you've only got
a handful of TTL I/Os to/from your "source"!

Problem is when you're given an interface that was *designed* to
connect one board to another INSIDE an instrument and then told to
extend it a couple of feet OUTSIDE the instrument (so the device
can be hidden to reduce clutter on the bridge).

THEN, told to make that *30* ft and denied a power supply at
the remote end of the cable!

"We won't be able to use PGDs because we can't deliver that
much power FROM THE INSTRUMENT.  And, all of the control logic
draws way too much current for the functionality it provides.
And, drop-in CMOS counterparts aren't available.  And, there's
way too much C in the cable for those TTL signals.  And you've
already committed to the aluminum castings for the case.  And..."

[The idea/feasability of using an MCU for such a function, back
then, was just plain silly!]

That's what happens when a company lets "sales/marketing" drive
their product development, unconditionally.  You need "adults"
that can make them understand the consequences of their fantasies!

OTOH, the salesman who boasted he could sell hundreds of these
"if you could extend the cable to 30 ft" was never heard from,
again!

[Valuable lesson learned.  There and at all subsequent employers
and clients, I did my own market research USING THEIR SALES RECORDS
to argue against the inevitable "kitchen sink" requirements lists
that invariably came along.  "Yeah, I know you, as a salesman,
don't want to lose ANY sale because of some missing capability.
BUT, you have to realize that these capabilities come with costs;
figure out the ESSENTIAL features and then learn how to spin those
to your customers!"]

So, I turned lemons into lemonade:  left the hardware run continuously
(eliminating the start-up delay necessary to "acquire signal") and
just turned the power switch into a "display blank" and "controls
inhibit" function.

But, the prototype board -- instead of being ready for production
for the previous design requirements -- had to be completely
redone (we had a small etch tank so we could print 2 layer protos
in-house so this was just an annoyance).

> seem to remember seeing a boost converter made from just a cmos gate and an 
> inductor, using the output as input and the supply pins as output via the ESD 
> diodes, but I can't find it again, but I found this
> 
> https://www.edn.com/efficient-voltage-doubler-is-made-from-generic-cmos-inverters/
> 
> 
> 

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Op-amp mystery liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2024-09-10 10:31 +0100
  Re: Op-amp mystery Don Y <blockedofcourse@foo.invalid> - 2024-09-10 05:27 -0700
  Re: Op-amp mystery john larkin <jlarkin_highland_tech> - 2024-09-10 07:47 -0700
    Re: Op-amp mystery Jan Panteltje <alien@comet.invalid> - 2024-09-10 15:05 +0000
    Re: Op-amp mystery Lasse Langwadt <llc@fonz.dk> - 2024-09-12 00:59 +0200
      Re: Op-amp mystery Don Y <blockedofcourse@foo.invalid> - 2024-09-11 19:00 -0700
      Re: Op-amp mystery john larkin <JL@gct.com> - 2024-09-11 19:10 -0700
      Re: Op-amp mystery piglet <erichpwagner@hotmail.com> - 2024-09-12 08:27 +0100
        Re: Op-amp mystery Jan Panteltje <alien@comet.invalid> - 2024-09-12 10:12 +0000
    Re: Op-amp mystery liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2024-09-12 13:21 +0100
      Re: Op-amp mystery piglet <erichpwagner@hotmail.com> - 2024-09-12 14:34 +0000
        Re: Op-amp mystery liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2024-09-12 18:03 +0100
  Re: Op-amp mystery John Robertson <jrr@flippers.com> - 2024-09-10 12:38 -0700
    Re: Op-amp mystery Don Y <blockedofcourse@foo.invalid> - 2024-09-11 12:15 -0700
      Re: Op-amp mystery liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2024-09-11 21:35 +0100
        Re: Op-amp mystery Don Y <blockedofcourse@foo.invalid> - 2024-09-11 18:37 -0700
  Re: Op-amp mystery legg <legg@nospam.magma.ca> - 2024-09-11 09:29 -0400

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