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Part Number: DAC8734
I have an DAC8734 set for a gain of 2 with output +/-15V. I have it set to 0V out (midscale). The DAC output is connected to a low-noise preamplifier that has a 100KHz low pass filter. When I measure the output of this preamp, I get 12 uVrms.
Is this expected? The datasheet spec is 40 uVrms in this band with a gain of 4, +/-10V out.
The 40µVrms is likely somewhat conservative, as well as a typical value. If you were in a gain of 4, you would probably see ~24µVrms. It is possible that our spec value included some noise from the reference we used to test the system. If you integrate the noise density (45nV/rtHz) over 100kHz bandwidth, you get about 14µVrms, which is about what you are seeing.
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In reply to Paul_Frost:
It's true that if you integrate the noise density over 100KHz you get 14 uVrms, but that ignores 1/f noise. So I would expect that with a gain of 2, the noise would still be much higher than 12 uVrms for a 0.1 to 100 KHz span. But if you think the spec in the datasheet includes some noise from the reference, as well as some extra to account for typical variation, then I understand.
In reply to Justin Scott:
It likely does. We do show 0.1 to 10Hz noise on the typical characteristics curve, which is maybe 4uVpp.
We specify the 1/f curve as about 500Hz. So it is at least bandwidth limited to that point (before broadband noise dominates).
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