Common mode voltage removal using new balancing technique for extraction of low level differential signals embedded in large common mode voltages

Abstract

The paper proposes a method based on new principle for removal of common mode voltages (CMVs) present in the differential signals#. These CMVs can be reduced nearly to zero without using any components with tight tolerances which is achieved using a new balancing technique. It is proved that the performance of the circuit depends only on the ratios and not on the individual values of the resistors because of which the performance of the circuit is not affected over the wide range of temperature. The circuit based on this principle was designed, constructed, tested and results are reported in this paper. Unlike the conventional techniques which use filters for removal of the common mode signals in specific band of the frequencies, the method reported here removes common mode signals of all known and unknown frequencies. Using this method, it is possible to extract very low values of the differential signals in the range of few microvolts where common mode voltages can be as high as few volts. It is possible to improve the effective common mode rejection ratio (CMRR) of any differential amplifier by a factor of more than 103 to 104 with this method.