amplifierdifferentialsignal-to-noisesnr
Often that the OPAMP has an internal noise of 1uV. If I have an extreme high gain of 10000, the noise will be amplified up to 0.01V.
Then, when I input a very low input signal of 10uV, after amplify 10000 times, it will measure 0.1V at the output.
According to typical SNR equation:
SNR (dB) = 20 * log ( Vsignal / Vnoise) = 20 * log (0.1/0.01) = 20dB
It yields a very low SNR of 20dB.
So, with the above mention, does this mean that my amplifier has a very low SNR characteristic?
"Signal Strength": I believe you are referring to the RSSI value, which is the Received Signal Strength Indicator this value is typically shown as a negative dBm value. RSSI is the measurement of power in an RF signal, the more power in an RF signal the better the connection quality is. It’s typically best practice to have the SNR value 20 to 25 dB’s away from the RSSI value. Please see the figure below, where it's also taken into account the Noise Level (-50 - (-96) = +46):
Yes, that's a reasonable approach, except that you'll also want to calculate the mean (DC bias) of your 10000 samples, and subtract that from the individual samples before you square them for the RMS calculation. This is equivalent to using a high-pass filter to block DC.
Best Answer
Your amplifier has average noise characteristics, the problem is that your signal is very, very weak. The amplifier is responsible only of the noise part of the SNR, so it has not a "poor SNR", but a "poor input referred noise".
To obtain a better SNR you can either amplify your signal, without adding noise, or reduce the noise.
Since amplifying without adding noise is quite a task I'd say that searching for low noise op amp is what you should do. A quick googling landed me right on the TI low noise amp page. As you can see there are sub \$\frac{nV}{Hz}\$ amplifiers, which may be a good start.
Please note that if your signal is low pass with a narrow band (such as and EEG) you need to consider also flicker noise and offset. If this is an issue you should really switch to an instrumentation amplifier that includes a chopping modulattor or at least an auto-zero or a correlated double sampling input stage. This first amp can help you give a boost to your signal, somewhere around 40dB, you can then add another stage to add the rest of the gain. Please note that in a multi stage amplifier the first stage is the most important noise wise, i.e. your second stage may be much more noisy than the first.