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I want to asking about Op Amp specification to realize thermal noise measurement on conductor. What the most important Op Amp specification for that application?What the specification for measure noise voltage and noise current is different?Can you give me example the Op Amps type which are appropriate for that application?
Whenever you use an op amp to measure the noise of something, the most important paramaters are:
The OPA211 is an example of a device with very low voltage spectral density (1.1.nV/rtHz). The current noise for this device is not optimized (3.2pA/rtHz).
The OPA827 has good voltage noise 4nV/rtHz, and good current noise 2.2fA/rtHz.
I highly suggest going through the noise precision labs videos. There are 9 videos and they cover a lot of detail on this subject.
Art Kay Senior Applications Engineer High Performance Linear
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In reply to Art Kay:
In reply to Saaddin Nur:
A common method used to measure low noise circuits is discribed in the TI design given in the link below. The key is to follow your amplifier with low noise amplifier that will boost the noise signal to a level you can measure with a scope. If you provide a schmatic of your circuit we can simulate this. You should definately sim it before you build the measurement circuit.
Attached is a good presentation that covers the subjects of chassis grounding, and PCB grounding. I think slides 39-41 are most pertinent to your question. I suggest looking through the slides and see if they help. Henry Ott has a very good book on the subject also “/Electromagnetic Compatibility Engineering”.
I read some of your OP Amp noise presentation. and learn that we use some gain and post gain amp to get the Amps noise plot in 0.1-10hz.
but, I'm confuse that, such like in OPA333 datasheet page1, there is a noise plot, the resolution is about 500nV/div, how we can get such low resolution of oscilloscope?
In reply to Haroad:
Regards,Collin WellsPrecision ADC Applications
In reply to Collin Wells:
Just to add to what Collin said. We have a TI Precision design reference design that covers this. See link below
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