The analog circuit is the actual interface between our product and the person that is being tested. Therefore its performance affects the performance of the whole product. Each analog circuit is responsible for one differential channel with two electrodes. The analog circuit is divided into a few parts which will be explained in this chapter. As was explains previously the signal we are interested in has an amplitude of about 10uV while the noise collected on the wires and on the electrodes has an amplitude of about 10mV. This means the signal Is about a 1000 times weaker than the noise. Therefore the main challenge of the analog circuit is to filter out the noise and amplify the signal.