Tesla MAB399, MAC199 voltage references

[jnd]

These are Czech made precision voltage references, accuracy is claimed to be basically same as the well known LM399 and LM199 respectively. But the question is how similar are they? They could be either licensed second source or simply clones or some kind of original product, probably inspired by the original parts to some extent.

To my knowledge only National and Linear ever made these references. Now Tesla is the third manufacturer. They are mentioned in 1989 catalog and the datecodes I've seen so far are all 1990. I'm not sure if there were any components made by licensing from American companies before the Velvet revolution which happened in late 1989. It's considered that all western equivalents were just more or less good clones. But it's known that in early 90's Tesla wanted to sustain the semiconductor manufacturing by making licensed power transistors, I think from Motorola.

If you check the specs between Nation, Linear and Tesla the parameters seems to be identical except the actual Zener Voltage. Both LM199 have 6.95 V typ. but MAC199 has 7.25 V typ., the tolerance range is similar but shifted higher. I just bought 5 of these and confirmed that they're indeed close to that value: 7.263; 7.254; 7.245; 7.252; 7.261 V (quick measurement at 0.54 mA). Package dimensions are different too, Tesla one has taller heat shield.

The more accurate version seems to be pretty rare and nowhere to be found except that one odd auction I bought it from. There are still MAB399 in one shop and I plan to buy some of those for more experiments, also cut one open and look at the die. I can't find any die photos of LM399, only of LTZ1000 So if you know about it or willing to sacrifice one LM399 for research purposes, let me know.

Tesla had long history of making Zener diodes in different kinds of accuracy, including reference grade and special TKZD (temperature compensated Zener diode) made for precision instruments, mainly or exclusively for Metra, another Czechoslovakian company (check this thread and photos there) so it may have something to do with choosing different Zener voltage.

Another question is how good is the long term stability. Unfortunately I don't have good enough meter to test and measure for myself. There is one value in the data book, -20 ppm, but it's missing for how long is that. I'll have to dig through my catalogs and data books at home to see if I can find anything more about these parts.

Feel free to discuss and speculate

[Mickle T.]

AFAIK there are other clones of the classic LMx99 zeners: chinese FW199 and russian 2S483