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| LM431 (TL431) 0.1-10 Hz Vp-p noise. |
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| magic:
That's 1100nV/rtHz at 10Hz, so 25 of them will match TI TL431 and about 300 will match onsemi. I don't know why onsemi is more efficient than TI, but as a general rule, noise is determined by the combined current of all references, not by how much you split that current into multiple chips ;) |
| iMo:
Sure, each reference with its own cathode resistor and combined via a summing resistors. As it is done with 399 when more pieces in parallel.. Thus 100 references, and 200 resistors (100*125k cathode ones and ie. 100*10k summing ones with 5V power) :phew: The total current will be ~2mA. PS: those 1150nV/rtHz is for 100uA, thus with 20uA it will be even more. Anyhow, simply scale it up to 1000 pieces, still only 20mA total current :D :D |
| magic:
--- Quote from: iMo on June 14, 2023, 09:11:45 am ---PS: those 1150nV/rtHz is for 100uA, thus with 20uA it will be even more. --- End quote --- You can try, but I doubt it. The first 10μA (LM385) or 400μA (TL431) flows through the bandgap reference, the rest is bypassed by a power transistor in parallel with it. Throwing more current at the chip increases power transistor bias and may reduce impedance and improve dynamic response, but I wouldn't expect much difference in noise. They all ought to be OK at their minimum operating bias. |
| jmelson:
A really good low-noise reference is the LM4140. Available with a few output voltages, noise is less when run from less than 4.5V, and you have to put about a 1 mA load on the output. There might be even better ones now, but we found this one to work really WELL in a noise-sensitive application. Jon |
| MasterT:
VN Output noise voltage(7) 0.1 Hz to 10 Hz 2.2 μVP Charts 11 and 12 show about 200nV/sqrt(Hz), compare to 48nV TL431B |
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