LEDs in parallel

Mine, too >:-} ...Jim Thompson

You're correct to assume so, I hang with the best!

At least you got something correct, for a change.

Jamie

:)

Me too. The unipolar ones are just, well, weird.

Which Colt motto? There seem to be a number of them.

I assume "It works every time!" (*)

Cheers

Phil Hobbs

(*)

So far, life has been a huge amount of fun. But what does that have to do with diodes?

The same as talking amps of current in a 1N4148. ...Jim Thompson

the

apt.

Naw, it is all you are worth. But it is fun to rag on your vainglory.

?-)

The datasheets I linked to go to 500 and 800 mA. Presumably those were pulsed measurements, but don't say so.

But what is a 1N4148 anyhow? I suppose JEDEC specs exist, but I've never seen one. And if JEDEC defines the part, where's the enforcement? What keeps some Chinese chop shop from shipping anything they care to call a 1N4148?

We have a number of cases where we have stock numbers for, say, a generic 2N7002, and another stock number for a Fairchild 2N7002, because sometimes it matters. It's safer to use a house number than a

I remember the classic 2N3055 fiasco, when people started selling tiny epitaxial parts in aluminum cans as "2N3055", and they tended to blow up.

Hmmm, I don't seem to use many 1N4148s. They appear on only about 10 of our 800 BOMs. The MELF version on even fewer. We do use a ton of BAV types.

Anybody know how, say, a BAV99 is defined and enforced?

Unfortunately you do indeed need to evaluate each vendor's version... in the mid '70's, at GenRad, I blacklisted Motorola's version of the LM324 as absolute crap. ...Jim Thompson

Which part are we being subjected to ?:-) ...Jim Thompson

Ummm... Performance.

You need to wonder?

That was a completely different animal. Money was to be made from that differential. It is a bit harder to make the smallest form factor glass diode (from the axial days). They have to fit inside the package and they have to work. It is a pretty tight window.

It, and the specs it had are one of the most commonly used diodes there is. It is a "small signal" purpose device, so all you surface mount and even integrated diodes would follow its spec to a degree as the switch from discreet TTL to integrated devices came to being. Of course the elements are far smaller now.

But the effect they had on the industry made its way into nearly everything you have.

Is it the 1N4148?

It is certain that the original maker released a spec and the contract fabs follow(ed) it. To easy to shoot oneself in the foot these days.

I doubt there is so much actual fakery going on as there used to be. Nowadays, they sell you outright failures that had zero cost attached.

Don't see many chips being reverse engineered anymoreeither.By the time they chop off the lid and analyze it, it is obsolete and the next great chip is out. It costs far too much to risk so many assets trying to reverse engineer a chip.

But a diode isn't a chip.

But a 1N4148 isn't that hard to make and get right either.

That took three days?

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.