Amplification of biosignals by body potential driving. Analysis of the circuit performance

A method for amplification of biosignals with asymmetrical amplifiers in the presence of mains interference is described. The common mode body potential is reduced by a body potential driver (BPD) circuit. A detailed model of the BPD circuit is analysed. A new quantity, residual impedance Z_r, which estimates the BPD performance is introduced. The influence of the BPD circuit parameters on the stability and Z_r are estimated so that optimal performance can be reached. Practical recommendations for the circuit design are given because controversial conditions must be satisfied to reach both the stability and minimum Z_r. The main advantage of the method is its simplicity, which leads to significant reduction of the number of elements as well as precision requirements in multichannel amplifier design.