Electronics > Metrology

Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x

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Kleinstein:
A voltage of 5.25 V to get a low TC suggsts that this would be for only 1 zener, and not with both zeners in seires in the usual compensation way.  It is normal to get a low TC for only 1 zener at a much lower current that for the series connection.

pico61:

--- Quote from: Kleinstein on May 13, 2021, 01:16:22 pm ---A voltage of 5.25 V to get a low TC suggsts that this would be for only 1 zener, and not with both zeners in seires in the usual compensation way.

--- End quote ---

Yes the experiments were carried out only on one of the two zener in the case and only on three, of the twenty 2DW235 purchased, with voltages that varied between them by a few tens of mV.

LHT5631080:
    Someone at 38HOT forum pointed out that it (2DW232) is more suitable for use under constant temperature conditions. The test conditions given in the specification are 25 degrees Celsius-75 degrees Celsius, which seems to indicate that it is not suitable for normal temperature use. Don't try to use a current far beyond its rated current in order to expect a TC.
    Under certain temperature conditions (for example, 50 degrees Celsius), a lower temperature coefficient can be obtained by adjusting the current around 5 mA-the test results of POCO61 have actually demonstrated this. 38HOT forum netizens make a voltage reference, and the 2DW232 internal 2 voltage regulators used in it are used in series instead of using one of them.

Kleinstein:
Using a stabilized temperature makes a lot of sense, as the 2nd order TC is relatively high. Even if one adjusts the current to get a low linear TC, this is only valid for a limited temperature range.

The 2DW232 have widely scattering parameter. So it is not like an 1N829 - more like a random pic from 1N821 - 1N827. For the series configuration it may just need a lot (too much also at a higher temperature) of current to get a low TC. Those diode are better used as single Zener with a lower current to get a low TC this way. So it depends on the units if they are more suitable to use as a single diode at a relatively low current or with 2 in series with compensation. There can be some that do not work well in both mode (e.g. need >10 mA in series and <<1mA as a single diode).
So ideally one would get better screed ones, so one knows which circuit there is suiteable for. The situaltion with the 1N821 / 823 is also not ideal - it may be nice to know if the TC is positive or negative, they are likely testing them and could keep them separate.

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