it is nV/SQRT-Hz, not nV/SQRT-100kHz or nV/SQRT-5kHz. That's "Hz" as in just one.
You are clearly not an engineer.
GK, you keep using units of "nV" for noise density, but nV does not specify noise density. You can't leave off the per part of the units
Input Noise Voltage at 1KHZ - less than 4 nanovolts
Where does the sqrt() part of the sqrt(Hz) come from?
I'm going to ask a dumb question after watching this guy's video.
Where does the sqrt() part of the sqrt(Hz) come from? I realize this has a simple answer to it, but for whatever reason its escaping me now.
Quoteit is nV/SQRT-Hz, not nV/SQRT-100kHz or nV/SQRT-5kHz. That's "Hz" as in just one.You are clearly not an engineer. That's the thing about "units".... unit means one. It's always one. It's kind of the point.
QuoteYou are clearly not an engineer.
S/he may not be an engineer but s/he is definitely an "engineer",
Apparently s/he is having lots of troubles understanding what a "density function" is.
QuoteInput Noise Voltage at 1KHZ - less than 4 nanovolts per stage
Those are impossibly nice specs,
I think I might be confusing you...
However, if you double the noise (measurement) bandwidth you don't get double the voltage when you measure the voltage at the higher bandwidth. The voltage will only go up by the square root of 2 or 1.4142. Hope this helps...
For us non engineers, please explain exactly what is either so remarkable or "impossibly nice" about the above quoted op-amp specification.
So I'm thinking this comes from the mathematics of adding (...summing, integrating, etc) incoherent phasors.
I would be extremely surprised if anyone would interpret it any other way unless they were being deliberately silly or awkward.
Wow, a week or so has passed and some people still struggle with density functions,
QuoteInput Noise Voltage at 1KHZ - less than 4 nanovolts per stage
Those are impossibly nice specs,
I don't know if this is your own special way of seeking help, but I should point out that persistently referring to oneself in the third person is typically a sign of some kind of psychological disturbance.
Is there any way this is real?
So I'm reading an academic paper today where the author claims a shielded DUT enclosure and preamp yield a "spectral voltage density S_u(f) of the background noise is 2x10^-16 V^2 s at 10 Hz."
To confirm... that's a -16 as in 0.1 femtovolts.
There's nothing special about his setup. Its a paper form the 1980's. He's using a 12bit / 20kHz A/D (controlled by turbo pascal ... ftw). Is there any way this is real? And if not, what mistake is he likely making?
So I'm reading an academic paper today where the author claims a shielded DUT enclosure and preamp yield a "spectral voltage density S_u(f) of the background noise is 2x10^-16 V^2 s at 10 Hz."
To confirm... that's a -16 as in 0.1 femtovolts.
There's nothing special about his setup. Its a paper form the 1980's. He's using a 12bit / 20kHz A/D (controlled by turbo pascal ... ftw). Is there any way this is real? And if not, what mistake is he likely making?
Messing around with low frequency VF opamps isn't really my thing but I can have a go at answering your question...
If you look at the units you have quoted then the number does make sense.
In my (RF) world I work in dBm/Hz for measuring the power spectral density of white noise. i.e. I measure the power of noise in a 1Hz bandwidth.
NOTE:
Power is a function of V^2
The period of a waveform is measured in seconds = 1/F(Hz)
So (in a 50 ohm environment) I could choose to convert the power spectral density units from dBm/Hz to (V^2)/Hz because I know I'm in a 50 ohm environment
or I could convert them to (V^2).s where s = 1 second = 1/(1Hz)
or I could convert this again from (V^2)/Hz to V/rtHz by taking the square root of both the top and bottom terms which delivers familiar units for opamp users.
Have a go at converting 2x10^-16 V^2 s across to V/rtHz to see if the number looks more familiar to you.
Note: in your example above at 10Hz you are close to the typical 1/f knee/cutoff in the noise response of a typical opamp aimed at audio use. So in this region the noise response won't be flat as it won't quite be in the white noise region.
It's late and I'm off to bed but I don't think you have worked that out correctly...