Low voltage zener diodes

Often, below 3V3, they were just a series chain of normal diodes. Nowadays a LED, with a sharp knee, works better if the voltage matches. Just beware using them at very low currents - they are light sensitive.

Arie

Am 08.10.24 um 11:24 schrieb Pimpom:

yes, that's true. At > 5V they are really avalanche diodes. Around 5-7V it is a mix. Zeners & avalanche diodes have a different TC, and it compensates at around 6V.

You can see the onset of avalanche behavior in the noise spectrum with rising voltage. True Zeners are much better here. For the BZX84 family:

Prof. Zener even sued the industry not to use his name for avalanche thingies because it was not "his" effect. They settled on Z-Diodes pretending it was for the V/I curve. But in the end the ghost was out of the bottle.

Gerhard

On a sunny day (Tue, 8 Oct 2024 14:54:39 +0530) it happened Pimpom snipped-for-privacy@invalid.invalid wrote in <sT6NO.84691$ snipped-for-privacy@fx11.ams:

Yes. These days there are 'bandgap' references, those are about 1.25V, extr3mely stable.

Yup. Soft knees and terrible tempcos.

Bandgaps like LM4040 are great. They get down to 0.1% and 50 PPM/deg C. 1.2 to 5 volts.

Everybody calls them all zeners now.

You can actually get a zener to oscillate.

An LED and a bipolar transistor and a source resistor can make a near-zero tempco current source. With free light!

Yeah, I like making a part serve a dual role. It's not just the money, it's the elegance.

I have a bunch of TL431, LM385 (1.25, 2.5 & adj.) and LM4040 references. But somehow these high precision, high stability references somehow feel like overkill in certain situations. It's not the cost, it's the appropriateness.

I remember the first time I used an LM385. I live in a very remote, very hilly part of India. 30-40 years ago, most of the rural areas in my state was powered by 300kVA diesel generators. The generators were made by an Indian company but the voltage regulators were imported and cost the then equivalent of about US$4-5000 to replace. Moreover, the manufacturer sometimes took months to supply a replacement.

So I designed and made several units for the state power agency, using only readily available parts. That's where I used LM385s as the reference. I had to make some of the parts by hand - like the EMI filter, the box, PCB, etc. The only material available then for weather proofing was small tubes of Araldite epoxy intended for domestic consumer use.

Yes, I have the LM4040A. But they're from AliExpress, so I wouldn't rely on the 0.1% accuracy. Got a small batch for US$0.10 each before India blocked access after the border squabble with China in 2020. I have no means of independently verifying the accuracy.

I also got an Aneng AN870 20000-count DMM with a claimed DC accuracy of

Checking the accuracy of one against the other would be like checking my digital scales with an uncertified weight.

Readings with the AN870 agree quite well with my Fluke 107. But the 107 claims only 0.5%. The $30 AN870 has *much* better features than the ~$100 Fluke though.

We had a long thread about that here many years ago. The concensus was that they didn't actually oscillate - an avalanche zener run a very low current had a finite chance of self-extinguishing the avalanche and turning it back on again when the next cosmic ray went past, which is what your pencil sketch seems to show.

Sounds interesting. What are the coordinates?

......<snip>..........

My house is at about 23.723°N 92.7173°E which is on the southern side of the state capital, a city of about 300K. The state is one twentieth the size of California, sandwiched along most of its north-south length between Bangladesh on the west and Burma to the east.

Most of the state is on steep hillsides, with few flat and level areas. The aerial distance to the sole airport in the state is about 14km and

Indigenous people make up roughly 90% of the population and have little in common with mainstream India.

Ah, so you’re one of those guys who used to come down from the hills and take over Burma periodically, the way the Elamites and Medes did to Sumer. Glad to know. ;)

Cheers

Phil Hobbs

:) :) Maybe we should do it again and kick out the military junta there. It wasn't too long ago that my people were headhunters! The state - with its 1 million citizens - is again being flooded by thousands of refugees from Burma fleeing the poverty and oppression in their own country.

I say 'again' because it was like this for decades before their brief stint with democracy. We give them shelter, food and employment, even ad hoc schools. They reward us with a sharp rise in crime - drugs, murder, robbery, scams, rape, human trafficking......

Lots of motorcycles driving on the wrong side of the street.

Looks like fun, riding on those hilly streets.

San Francisco is hilly too. Kamakazies skateboard down the hills.

Just admit the women. They are less dangerous.

..........<snip>...........

Well, we have a motorbike gang of sorts here, exclusively for owners of 'Bullet' bikes, a kind of poor man's Harley. Members look tough in leather and denims, sport beards and take rides and out-of-state trips. But they're completely harmless. They donate blood, contribute to charity and volunteer in emergencies. I have several friends in the 'gang'.