EXG Pill SPICE Simulation

[NNNILabs]

I took up the task of simulating the EXG pill in LTspice, and this issue thread will be updated as I make progress. For now, I have tested the low-pass filter section, albeit with ideal components, with the following results. The -3dB points are at 0.25Hz and 50Hz. Further simulation will focus on using the correct part model, and simulating the instrumentation amplifier part of the circuit. One important thing to note is that the selected part, the TL074, has an input common mode limitation, the inputs must be at least 2V (or ideally 4V) above the negative rail.