> Management was griping over having to pay $0.28/piece @ 2500qty. for the =
-55C rating
> in a quad op-amp; to use a single $2.00 op amp would probably take quite =
a bit of fight.
>
> The LM124 was chosen because it is a "jelly-bean" op amp.
> (1) it will probably be available in some form the next 30 years (hard
> requirement) - the bar is set *really* low for a pin compatible replaceme=
nt to be put in.
> (2) it is cheap
> (3) it is rated for -55C operation
> (4) it is "HV" rated. We are using a 15V supply that may be subject to tr=
ansients.
>
> The issue is that I can't push too hard against the limitations of the LM=
124, I don't want
> batch/manufacturer specific behavior. So I will have to figure out a way =
around the slew
> rate. Probably by reducing the PWM triangle wave to 1V peak-to-peak.

OK, so as you have discovered the slew rate is typically within spec at a s=
pecific temperature, with no limits in variation given.

How is management going to react when you point out that it is probably goi=
ng to cost $5/chip to have them lot tested to be within spec over the whole=
 temperature range, and when another lot is purchased for next years produc=
tion they will need testing as well, especially if they are from a differen=
t manufacturer. This is the only way that you are going to be able to guara=
ntee that the equipment will keep operating.

But when I see a spec that wants full military temperature range I have to =
ask just what is the end use.

And this 30 years business, is that 30 year operational life for the first =
ones off the line, or is there going to be production of this product for 3=
0 years, or ... Somewhere along the line to reach any of the 30 year requir=
ements money is going to need to be spent in ways they haven't imagined, li=
ke having the PCBs (and other bits) built to NASA/ESA build standards for r=
eliability ...

Sounds like they want a $10 Voyager spacecraft ...




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