On Sat, May 3, 2025 at 01:07 PM, thet wrote:
the datasheets don't use exactly the same terms.
is "equivalent input noise voltage" the same things as "voltage noise density"?
The latter term is more correct, but they actually are the same. The give-away is the identical units.
TLE2071 gives "Equivalent input noise voltage" as 12nV/¡ÌHz
I thought I read 17. My mistake.
OPA1641 gives "Input voltage noise density" as 5.1 nV/¡ÌHz
if those are the same thing then the difference is more like 7dB, so still not great.
Well, 7dB can be a lot in a direct comparison.
for comparison regular old TL071 gives "Input voltage noise density" as 37nV/¡ÌHz
That's right. That's why the TL071 was never used in low-noise applications.
is this the relevant noise spec for the very high impedance applications?
It is definitely. Although Noise Current Density can be quite significant in Hi-Z applications.
A more thorough evaluation would imply calculation of both voltage density and current density effects, in addition with thermal noise of sources.
