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Maciel
Maciel
6/30/2013 5:38:26 PM
User Rank
Newbie
Re: Is it really that hard????
Several times we had to stop and analyze the layout, until I began to trust more in charge of the layout, then I taught him to analyze the data sheets and how it should be done mainly ground planes.

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Ranasinghe
Ranasinghe
6/30/2013 12:38:51 PM
User Rank
Master
Re: Twas ever thus?
Very true Natcrawl, it Is a compulsory that companies should always lock at the continues development of the technology in order to survive w in the very competitive market.  

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WKetel
WKetel
6/26/2013 1:41:35 PM
User Rank
Artist
Re: Is it really that hard????
It was quite a challenge the most recent time, when the PCB layout designer really did not know between op-amps and apple dumplings. At that point it would make more sense for the engineer to do the layout and then the PCB expert check for rule violations. But that did not happen, instead we just kept correcting the problems. Tedious but effective.

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Brad Albing
Brad Albing
6/26/2013 12:26:07 PM
User Rank
Blogger
Re: Is it really that hard????
@WKetel - Which is why the design engineer should be looking over the shoulder of the layout guy. Tedious - maybe even annoying - but it leads to higher quality results/fewer respins.

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Brad Albing
Brad Albing
6/26/2013 12:23:20 PM
User Rank
Blogger
Re: designer supplied models
@Scott - and you're just scratching the surface there with complicating factors.

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WKetel
WKetel
6/25/2013 6:03:39 PM
User Rank
Artist
Re: Is it really that hard????
It seems that I forgot to even mention the designing of printed circuit boards, which is where those opamps and other things live. I hav gone through one company circuit board rule book and my conclusion is that if the board designers know nothing about the corcuit being laid out, then probably that 250 page document is appropriate, but if the same person who designed the circuit is doing the layout it may work well with only a minimum of rules. Understanding the circuit probably trumps any number of rules, since exceptions almost always arise, and the layout drafter probably does not have a clue. I know that was the situation when I worked at Methode. One artwork person understood electronics well enough to know to ask for explanations, the other person did not have a clue and was convinced that the rules covered everything. They sort of did, except for the certainty of first-spin success.

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Scott Elder
Scott Elder
6/25/2013 11:02:25 AM
User Rank
Blogger
Re: designer supplied models
<<I guess it depends on how far you are pushing the op amp parameters.>>

That's certainly one aspect.  But then what about things like rejection of power supply noise into the signal path.  Stability if the load is reactive.  Settling time driving an ADC input.

The list can be pretty long.

 

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Brad Albing
Brad Albing
6/25/2013 10:35:23 AM
User Rank
Blogger
Re: Is it really that hard????
OK - this helps clarify. We should discuss further in the context of blogging.

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audiocal
audiocal
6/25/2013 10:15:59 AM
User Rank
Teacher
Re: designer supplied models
I guess it depends on how far you are pushing the op amp parameters. We always design a minimum of one decade of gain and/or bandwidth away from the GBW limit, usually more since we don't have really high frequency requirements. For these cases the SPICE macromodels work fine to show any gross design errors. We make a well-educated guess as to the parasitic capacitance across the op amp inputs and cancel the phase margin reduction from that with a feedback cap across the feedback resistor. This conservatice design philosophy works well for both SMD and thru-hole PCB layouts.

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WKetel
WKetel
6/24/2013 9:44:56 PM
User Rank
Artist
Re: Is it really that hard????
Aside from switchmode power supplies and chargers for the various Lithium battery types, we have motor and solenoid drivers and all manner of audio amplifiers. Also a wide realm of RF systems, including power amplifiers and very low noise receiver systems. Then there are those amplifiers and controls associated with instrumantationthat must be DC accurate as well as having perfectly linear response up to frequencies inthe KHz range. All of this aside from the realms of "consumer products". These are all in the industrial arena, not produced in quantities large enough to merit an ASIC. Some not built in quantities karge enough to merit a circuit board design.

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