Question about mV/nA signal amplification to detectable levels

Thread Starter

Lobware

Joined Mar 26, 2022
1
Hello,

I'm relatively new to PCB design and currently am working on a research project that requires me to design a relatively complex board that can amplify about 100 different mV/nA signals non synchronously. the signals are coming from neurons, and I'm currently stuck on selecting the correct opamps/preamplification circuits/EMI filters to use in array for such high EMI-risk signals.

from what I've gathered, the signal intensity of a neuronal action potential hovers around 10-100mV and 10-100nA.

Id appreciate any help immensely^^
 

MrChips

Joined Oct 2, 2009
27,635
Welcome to AAC.

10mV signals is not in the hard to detect range.
10mV/10nA suggests source impedance of the order of 1MΩ.
Your challenge will be to minimize external interference.

What you need to research is differential op-amps with high input impedance.
Look up instrumentation amplifiers (INA).

1648341879657.png
 

Papabravo

Joined Feb 24, 2006
19,551
I am a bit confused about what you mean by "high EMI-risk" signals.
One of the major methods of isolating signals of interest from other interfering signals is by frequency. It seems probable to me that signals from biological sources are unlikely to much above a few kilohertz. This means that pretty much any part you select will be able to perform adequately. In most circuits you will depend on the passive components rather than the semiconductors to achieve acceptable levels of performance. The only other advice I can give is don't try to raise the signal levels with a single device using a large gain.

EDIT:
Vis-a-vis the Instrumentation Amplifier (INA) mentioned by @MrChips, here is a simulation using a discrete version of an INA with TL072 opamps for measuring small temperature changes. It shows an example of how to set the gain.

1648342562023.png
 
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