hello I need a OPAM work with a signal that is highly noisy frequents a range of 100Hz to 20KHz to let me do this filtering . The signal has an amplitude of 5nV peak .
Because your signal amplitude is so small, it could easily get drowned by the offset of the device. For this application, I recommend that you use an instrumentation amplifier because these devices are specially designed to amplify very small voltages in noisy environments. We have a couple of these in our portfolio, so I was hoping you could be more specific about your application: What will your input signal be coming from -- a sensor? What supplies do you plan on using, single or dual?
Hi Kris Tks for you answer.
The signal it´s BioSignal from surface electrodes, it´s dual in +/- 12 V. I initially using an AD620 in the initial stage but for filters I would like a recommendation for OPAM since I 'm using OP07 OPAM ( for filters and gain) and I'm not sure if it is the best choice. You understand me ?
Can you confirm that the signal amplitude is 5nV? Are you looking at the frequency domain? It seems like this is too small even for biopotential signals.
Hi Kris ! Course if the signal amplitude is 5nV and is a biosignal . It is very small so I'm looking for help and effectively 'll use in the frequency domain but first I must amplify and filter a range of volts.
Hi Oscar , You need to do more study on the nature of electrical noise.
Basically the intrinsic Boltzmann (Johnson) noise of a 1kohm resistor at 1Hz measuring bandwidth is 4nV at room temperature.
For 100Hz bandwidth, the noise is sqrt(100) or 10 times higher e.g. 40nV.
To measure 5nV signal at 100Hz or more you need to
(a) lower the operating temperature to liquid nitrogen or lower
(b) lower the source resistance (difficult with bio signals)
(c) take multiple measurements and average them, this only works if the biosignal is an evoked potential, i.e. a response to a signal you inject somewhere else. The improvement goes as the square root of number of measurements, so you can get noise down to 4nV at 100Hz by stacking 100 samples.
So once you have a measurement setup where the signal is more than Johnson noise , you can start thinking about op-amps. This is a fundamental limit of the laws of physics.
If you want a starting point , look at the OP27 , thare are a lot of low noise appnotes published that refer to this device.
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