PASSIVE CIRCUIT FOR IMPROVED DIFFERENTIAL AMPLIFIER COMMON MODE REJECTION

摘要

A novel passive circuit for providing improved common mode rejection of a differential amplifier novel. The passive circuit functions to compensate for amplitude mismatches between the two outputs of a differential amplifier. To compensate for the amplitude mismatch between the output traces of the amplifier, a resistor is inserted in series with at either one or both of the differential outputs. The values of the resistors are set such that the mismatch is substantially eliminated. Inductors are connected in parallel with the resistors to create a zero ohm path for power. At high frequencies the inductor impedance is sufficiently high that the series resistor compensates for the imbalance caused by spurious products. The imbalance in the amplifier outputs is corrected with the resulting increase in the rejection of spurious frequency products by exploiting the differential common mode rejection (CMR) effect of the differential amplifier.