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Neither.Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Thanks,
Paul
That's 1.3nV times sqrt 0.01Hz. But one has to ask how the 0.01HzCould someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Note that op amp noise depends very strongly on frequency band andHi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Thanks,
Paul
Linear Technology has some outstanding tutorials on this.
Source impedance, very interesting. Thanks for the information Don.Note that op amp noise depends very strongly on ... and source impedance.
pmlonline@gmail.com wrote...
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
That's 1.3nV times sqrt 0.01Hz.
Sensitivity of a rf pickup system is swamped by terrestral noise belowWinfield Hill wrote:
pmlonline@gmail.com wrote...
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
That's 1.3nV times sqrt 0.01Hz.
Thanks, it makes sense. So at 0.01 Hz bandwidth it comes to 130pV.
Where does the noise come from? Is it purely thermal or just a
byproduct of the amplification process?
Here's my problem. I am trying to get a rough guestimate of the values
to see if it is even plausible. I am estimating that a signal will be
picking up ~ 1pV of RF at 37Hz on a coil. I guess it would take a
differential amplifier fed into another differential amplifier. If the
gain of each amplifier is 1E+6 than that's a total gain of 1E+12. Wow!
The device will be out and away from the city and will contain a
second nearby coil to cancel as much RF noise. So there would be two
coils-- the RF coil and the noise cancellation coil. I believe that if
the output from noise cancellation coil is properly adjusted /
calibrated that it can cancel out the RF noise from the output coil.
So if we can get the RF noise low enough then what is left? Thermal
noise? Also I would know the phase of the 37Hz signal. Could that be
an aid? The end goal is to design a device that can tell if the 37Hz
1pV signal is on or off. Is this doable? I think time is on our side.
That is, if we build a filter with high enough Q then it could detect
the signal. The problem is that the Q would probably have to be so
high that it may take a long time for the signal to rise above the
noise. Hopefully some clever math technique, possibly taking advantage
of the known signal phase, can bring the detection time under a minute.
I've worked with FT functions before, but off hand I don't see how the
phase would help that much. What if the 37Hz signal could be modulated
at say 3.7Hz? Could that help somehow?
I really appreciate any tips,
Paul
These 1.3nV/rtHz apply to 100 Ohms or so. It'll be muchDon Lancaster wrote:
Note that op amp noise depends very strongly on ... and source impedance.
Source impedance, very interesting. Thanks for the information Don.
I'll have to read up on that. I'll be dealing with high impedance.
Beware of the noise figures in the data sheet. They may not apply atHi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
He is trying to receive a RADIO signal at 37 Hertz.pmlonline@gmail.com> wrote:
Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Beware of the noise figures in the data sheet. They may not apply at
such low frequencies where 'flicker noise' often predominates. (A
Nuvistor can sometimes out-perform modern semiconductors for low LF
noise)
If the option is open to you, it is often more cost-effective to improve
the level of signal pick-up, rather than trying to get ever nearer to
perfection in the amplifier.
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Beware of the noise figures in the data sheet. They may not apply at
such low frequencies where 'flicker noise' often predominates. (A
Nuvistor can sometimes out-perform modern semiconductors for low LF
noise)
If the option is open to you, it is often more cost-effective to improve
the level of signal pick-up, rather than trying to get ever nearer to
perfection in the amplifier.
He is trying to receive a RADIO signal at 37 Hertz.
By a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input stage.
Unless everything is in an anechoic fully shielded room.
His budget and effort would be best put into making the aerial moreAdrian Tuddenham wrote:
pmlonline@gmail.com> wrote:
Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Beware of the noise figures in the data sheet. They may not apply at
such low frequencies where 'flicker noise' often predominates. (A
Nuvistor can sometimes out-perform modern semiconductors for low LF
noise)
If the option is open to you, it is often more cost-effective to improve
the level of signal pick-up, rather than trying to get ever nearer to
perfection in the amplifier.
He is trying to receive a RADIO signal at 37 Hertz.
By a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input stage.
Unless everything is in an anechoic fully shielded room.
Don Lancaster <don@tinaja.com> wrote:
Adrian Tuddenham wrote:
pmlonline@gmail.com> wrote:
Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Beware of the noise figures in the data sheet. They may not apply at
such low frequencies where 'flicker noise' often predominates. (A
Nuvistor can sometimes out-perform modern semiconductors for low LF
noise)
If the option is open to you, it is often more cost-effective to improve
the level of signal pick-up, rather than trying to get ever nearer to
perfection in the amplifier.
He is trying to receive a RADIO signal at 37 Hertz.
By a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input stage.
Unless everything is in an anechoic fully shielded room.
His budget and effort would be best put into making the aerial more
directional.
At that frequency, spaced aerials and a correlation technique might be
the way to go.
LOL. A 60dB parabolic at 37Hz .... Lambda is around 10'000km ...Adrian Tuddenham wrote:
Don Lancaster <don@tinaja.com> wrote:
Adrian Tuddenham wrote:
pmlonline@gmail.com> wrote:
Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Beware of the noise figures in the data sheet. They may not apply at
such low frequencies where 'flicker noise' often predominates. (A
Nuvistor can sometimes out-perform modern semiconductors for low LF
noise)
If the option is open to you, it is often more cost-effective to
improve
the level of signal pick-up, rather than trying to get ever nearer to
perfection in the amplifier.
He is trying to receive a RADIO signal at 37 Hertz.
By a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input
stage.
Unless everything is in an anechoic fully shielded room.
His budget and effort would be best put into making the aerial more
directional.
At that frequency, spaced aerials and a correlation technique might be
the way to go.
A parabolic reflector with a 60 decibel gain might do the trick.
Tiny problem with zoning, though.
For those who are very interested in low noise at lowish frequencies:Hi,
Could someone so kindly tell me exactly what 1.3nV / Sqrt(Hz) @ 1KHz
means on a differential amp spec? What would the noise be between
37.00 Hz and 37.01 Hz? Would it be 1.3nV / Sqrt(37.00 - 37.01) or
1.3nV / Sqrt(37)
Yes, using the 1PPS pulse from a GPS you could keep the systems in sync toAt that frequency, spaced aerials and a correlation technique might be
the way to go.
Don, after further studying, I believe that I can cancel out nearly allBy a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input stage.
Thanks Ken. I found a great pdf file on noise,For those who are very interested in low noise at lowish frequencies:
Take a look at the company called "interfet" in Texas. They make JFETs
with a noise of about 1/4 nV/sqrt(Hz).
Yes, great idea. I was thinking about that yesterday. Although IYou can also get that level by putting 16 LSK170s in parallel.
Don, after further studying, I believe that I can cancel out nearly allBy a conservative estimate, the manmade and terrestrial noise at this
frequency will be something like 170 decibels ABOVE the ktb noise.
It does not matter in the least which device he uses for his input stage.
Thanks Ken. I found a great pdf file on noise,For those who are very interested in low noise at lowish frequencies:
Take a look at the company called "interfet" in Texas. They make JFETs
with a noise of about 1/4 nV/sqrt(Hz).
Yes, great idea. I was thinking about that yesterday. Although IYou can also get that level by putting 16 LSK170s in parallel.
Resistors up to a few Gohms can be bought. They introdude very littleThanks Ken. I found a great pdf file on noise,
http://eesof.tm.agilent.com/docs/iccap2002/MDLGBOOK/7DEVICE_MODELING/6NOISE/NOISEdoc.pdf
In considering the JFETs as an amplifier, wouldn't I have to use
several resistors? It seems that resistors are a definite source of
noise, which would add to the 1/4 nV/sqrt(Hz) JFET.
Try this:You can also get that level by putting 16 LSK170s in parallel.
Yes, great idea. I was thinking about that yesterday. Although I
didn't know that it was also the sqrt() of total parallel devices.
Isn't paralleling equal to multiple sampling? Consider a computer
program that does averaging. Say we take 10 samples, sum up all 10
samples, and take average signal. I thought that 10 averages would
decrease random noise by a factor of 10.
Ideal inductors are noise free. The resistances of an inductor make noiseDoes anyone have any input on the following idea? According to the
above pdf, Inductors are considered fairly noise free. Perhaps that
pertains to well made L's. I have not verified that.
Your frequency is kind of low but take a look at Triad's or Tamura's smallIf that is true
then a transformer should also be fairly noise free-- say a nice
toroid.
Think more along the lines of getting up to 10 to 100 times not hundreds.Why not amplify the signal to say a few hundred times with the
transformer and then use a differential amplifier?