| Electronics > Projects, Designs, and Technical Stuff |
| Replacing Zener with vreg? |
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| TERRA Operative:
I'm currently in the process of recreating an unobtanium option board for my HP LCZ meter and I am stuck on one part. In the top left corner of the schematic below, there is a 6.3V 1%, PD=0.4W, TC=0.001% zener diode. I'm having trouble sourcing a zener of this type, is it possible that I could stick a vreg here instead? I think it shhhoouulldd be relatively simple to drop in a vreg set to 6.3V, but I just want to get someone more knowledgeable to make sure there's not a trick hiding in there. :) |
| Whales:
--- Quote ---TC=0.001% --- End quote --- That sounds crazy grade. 0.001% = 1e-5. Is the opamp it connects to even that good (eg in terms of offset voltage, tempco)? I don't see any trimmers on the resistors either, so I can't imagine this needing that high of a spec. Typo? I could still be wrong, but I'm suspicious given the schematic has no further info. Sidenote: there are variable voltage references available. Cheapest is something like a TL431, but it doesn't meet the above tempco spec :P |
| TERRA Operative:
Yeah, I was wondering about that... The part is CR1 in the pic below. The AD7530LN is good for 2ppm of FSR/oC according to the datasheet. I haven't looked at the TL074CN, but here's the datasheet: http://www.ti.com/lit/ds/symlink/tl074.pdf |
| iMo:
It could be an 1N828/829 there, for example (0.001-0.0005%/C). I think any regulator with tempco <50ppm/C will do.. |
| TERRA Operative:
--- Quote from: imo on November 09, 2018, 05:06:09 pm ---It could be an 1N828/829 there, for example (0.001-0.0005%/C). I think any regulator with tempco <50ppm/C will do.. --- End quote --- That looks like a 6.2V zener, would that be ok to use instead of a 6.3V? It looks like the HP part number (1902-0692) cross references to the JEDEC part number DT790107A but I can't find anything on that number online beyond HP cross references. |
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