A novel approach to the design of a Wilson referenced ECG amplifier

The Wilson Central Terminal consists of three limb electrodes connected through a resistor network at the inverting input to the ECG amplifier. It is often used as a zero potential reference in ECG recordings. In this paper, the implications of using a Wilson central reference on the overall amplifier's common-mode rejection ratio and noise specifications is analysed. It is shown that the Wilson reference can degrade the overall amplifier specifications. The design of a Wilson referenced amplifier is then described which shows this to be true. A novel approach to the design of a Wilson referenced ECG amplifier is then presented, whereby the reference network is moved from the input to an intermediate stage of the amplifier. An analysis on the improvements achieved over the conventional approach is given. An amplifier design using the new approach is then described. Tests results showed a significant improvement in amplifier common mode rejection ratio and noise specifications when compared to the conventional design.