LEDs in parallel

Rohm RLS4148 is the MELF we use. But production prefers SOT-23 parts, and you get two per can, with the second diode free or less.

MELFs do have essentially zero inductance and good thermals.

Do you talk like that in real life?

I didn't even notice the [mv] typo. It was obvious from the numbers that the value was volts.

Well, that hasn't happened in this thread.

But what does "have to" mean? Is there any enforcement?

How would you use it a a VVR in reverse mode?

A diode isn't a tool, it's a part. And the curves are all over the place.

The tempco isn't the issue so much as the repeatability. But most LEDs have low or positive TCs at operating current. Many of the modern white super-bright LEDs are many chips on a common aluminum substrate, in series-parallel arrays, with no resistors.

If you look at Fairchild's fig 6, you can see the lines converging. This plot stops at 20 mA so they don't show you where the lines cross, namely the zero TC current.

On NXP's fig 3, the typicals cross at about 1.3 volts, 450 mA. I wonder if most silicon PN junctions have their zero TC point around

It works for me!

No content, as usual.

But their JAN version was probably fine.

Hey, YouTube lets you see the Super Bowl commercials without making you watch the game!

I don't see how there could be. It just has to comply with its *own* datasheet, it is surely up to you to compare the datasheets of the various manufacturers.

I have just now been trying to spot the difference between two LT1013 opamps, TI and (the original, presumably) LTC,

The LTC one is 3 times the cost. It seems to have a couple of guaranteed limits that the TI one does not.

ICs could be a different situation from generic diodes, I suppose there is more likelihood the actual design is licensed there. Jim and miso would know.

Crazy old hen.

Things like 1N4148 are JEDEC numbers. I was wondering if compliance is entirely voluntary, and if anyone here knew how the JEDEC standards thing works.

Under US law, a part number can't be copyrighted. Absent patent protection, nothing stops anyone from making and selling LT1013's.

I could be licensed, or it could be a functional look-alike. Once upon a time I designed an SSI look-alike for a National hard-drive controller chip, strictly black-box... I had no knowledge of the actual circuitry of the National part, and absolutely no prior experience in designing hard-drive controllers :-)

Working strictly from a performance specification I exceeded the National chip's performance in all respects ;-) ...Jim Thompson

Cool, I did not know that.

Excellent!

If anyone wants a good deal on LT1013CP I have a large quantity for sale.

Don't worry about the funny markings - "LM358" is just our stock code.

How could I know how your flashlight works?

You could find out and tell us. That could be interesting, especially the non-invasive ways. There could be all sorts of interesting tangents. Really.

Go for it.

Hey, Phil,

Suppose Nimmie is right, and his LED flashlight has a 555 or equivalent, and it - for some reason - modulates the LEDs all the time. Or maybe it has a switcher or equivalent. Now the light from millions of flashlights, all over the world, is modulated. Possibly detectable from satellites, certainly from drones. Implications.

When I was a kid, I had a cardboard tube with a lens and a PMT, and I used to listen to light. Mostly I got 120 Hz and the occasional lightning bolt. Things would be much more interesting nowadays. Add a sampling downconverter to get the supersonics, maybe.

It was a little more subtle than that. The original 2N3055 used a single diffused mesa 'hometaxial' process that produced a large and rugged but leaky part - needing extra guarding/sealing at edges to prevent leakage. The parts produced by this process were also heavily evaluated for avionics and space applications.

As Epitaxial triple diffused processes advanced, parts were fabricated with roughly the same book ratings in the reduced wafer size that the new process permitted, due to reduced edge guarding. They were cheaper to make using the new process, and could be easily adapted to plastic packaging.

The new parts were not as rugged as the old, due to increased Rthjc, reduced forward biased safe operating area and secondary breakdown characteristics - but they eventually obsoleted the old parts for the reasons previously mentioned. This was not true immediately of all the original mesa part type numbers - just the ones with cut-throat consumer application/demand.

During the changeover, the older technology was sometimes identified by a part number suffix and eventually became associated with 'unprogressive' wafer fabs. The last 2N3055H mesa parts I was ever forced to purchase in volume were made in Yugoslavia, at a small fraction of North American book prices. This was probably a result of distortions in currency and iron curtain exchange, but it prevented justifying the adoption of more easily processed modern plastic parts in a new design's bottom line. No doubt reality set in at some later date....

RL

My experience was going from RCA to Fairchild 2N3055's. The Fairchilds were much faster, much lighter, had maybe 1/4 the chip area, and blew up a lot.

excuse.

It was part of the mil spec, and since COTS, is not valid or implemented any more.

Unless they claim like operation or tout it as a replacement.