He is. He told you Motorola performed the matching and culling at the time of manufacture. It has nothing to do with "coming off the same die", or anything else. It has to do with REAL performance AFTER manufacture. And they culled together matched sets based on REAL performance numbers.
You are apparently in the dark a bit more than you think you are.
Hardly insider information. When else would they possibly do it?
It has nothing to do with "coming off the same
It sure does. Parts off the same die tend to be very similar. More so nowadays, since silicon processing has improved a lot in the last few decades.
I find that small parts, like LEDs, tend to be very repeatable, especially ones off the same reel. We once made a deal with Mouser to sample us ten parts each off a bunch of different reels of rectifiers, with the understanding that they would test the samples and they would then sell us the reels that we liked, for Grehkov (drift step-recovery diode) use. That worked great. Parts from different reels were very different, but we fould one reel that had all good snappers.
It has to do with REAL performance AFTER
Duh.
Well, I do this for a living, and build stuff that works.
no, ^^^^ we did the testing
What did you measure?
Electronics is irrelevant to you?
The LT Spice model for the 1N4148 has an Rs value of 0.568 ohms, which looks a tad low to me.
What current did you measure on the 1N4148?
Then why take a stupid stance that they do not need to be thermally coupled?
I explained that. At low currents, diodes have negative TCs and can go into thermal runaway if paralleled (and, obviously, poorly heat sunk.) At high currents, they become ohmic and have more positive TCs, so there's no thermal runaway mechanism.
That's why people sell flashlights that have multiple LEDs and no resistors. Because it works.
And multiple diodes soldered to a common heatsunk baseplate really aren't "thermally coupled" very well... not much better than if they were separate diodes on the same heat sink.
Whether diodes can be usefully paralleled is an engineering issue that has to be evaluated for specific cases. But a hard rule to never parallel diodes, because you heard it somewhere, doesn't make sense.
Thermal runaway is a bigger issue for transistors.
That's the static resistance. A more useful value is dV/dI, the slope of the curve in the linear region. That's the Spice 0.568 value. The value from several 1N4148 data sheets is more like 0.7 ohms.
LT Spice shows 0.64 amps at 1.236 volts. Most diode data sheets show about half that current.
You don't actually care about diodes, you just want something to whine about.
And you guys call *me* a troll?
I have PCBs with 30 LEDs and limit resistors on it. Powered by a 12V
6W dongle.I posted a hi res pic of them on flickr.
Switch famous to infamous and the description of yourself is all too apt.
?-)
After almost a week of brooding, that's all you can come up with?
You connected LEDs and resistors?
Arguing with Larkin is like arguing with a liberal, they're all mouth and no math. ...Jim Thompson
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