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I'm developing an application that sends an electrical signal to the human body. It is a bioimpedance system. This signal has approximately 3.2Vpp ranging between + 1.6V and -1.6V, at a frequency ranging from 50KHz to 100KHz, with 1mA of current.

This signal is sent to the Human body and received through an instrumentation amplifier (INA118) as in the following image:

enter image description here

This signal after being amplified by the InAmp goes to a 12bits (0 - 5V) AD converter. I am feeding the InAmp reference pin with a voltage of 2.5V (Vdd / 2) to give an offset gain in the signal.

The current that should circulate in the whole body, right? As in the following image:

enter image description here

My question is: How do I set the gain of my Instrumentation Amplifier? What is the average voltage drop my signal will have going through the human body? I need to set a value that works for as many people as possible who will use my system.

Thank you! Regards,

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  • \$\begingroup\$ if your current source only produces 1.6V peak you may not get 1mA flowing in the circuit, also 1mA will be quite uncomfortable. \$\endgroup\$ – Jasen Aug 26 '17 at 23:12
  • \$\begingroup\$ @Jasen, won't be a problem at that frequency \$\endgroup\$ – Scott Seidman Aug 27 '17 at 3:00

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