Currently I'm designing a pre-amp for detecting nanovolt-scale(~100nV, <1kHz) signal for experiment. I need a final gain to be around ~100000. Since the magnitude of the signal is extremely small, noise control is the major issue. So I am considering using AD8428 low-noise, fixed gain(G=2000) instrumentation amp (https://www.analog.com/en/products/ad8428.html) as the main amplifier and get some additional ~50 gain.
The two major options that I am considering to get the additional gain are,
- A subsequent AD8429 low noise variable gain in-amp
- PGA in ADC
And I have two questions.
Is using in-amp(AD8429, https://www.analog.com/en/products/ad8429.html#product-overview) to get additional gain rather than using PGA is the better option in terms of noise-control? Or is there any other recommendation?
If using additional in-amp is the best option, how should I stack them? It's hard to find a good method to stack two in-amps. Is there any good example?
I appreciate any advice you might have.