I would like to request some help in analyzing the op-amp circuit used by SparkFun here. I'm particularly interested in the pre-amplifier portion of this design.
The write-up included by SparkFun mentions an arithmetic gain of 100. When I simulate this circuit with LTSpice and provide a 10mV 8kHz AC sine wave signal as the input, the output I am getting is ~0.55V 8kHz sine wave. How can this be? I would expect an output of ~1V 8kHz sine wave.
A screenshot of my spice setup is below, I'm using standard part values from the built-in libraries on LTSpice: