A fully-differential DC restoration circuit

Modern instrumentation is moving towards fully differential conditioning circuits. They provide an elegant and efficient way to adapt differential signals, like those provided by balanced sensors, to differential-input analog-to-digital converters (ADC). For that to be possible, many well-known Single-Ended (SE) conditioning circuits must be converted to their Fully-Differential (FD) versions. This work presents a FD dc servo circuit, able to restore both common mode and differential mode dc levels to their desirable values, suited to those required by the ADC to optimize its input range. The general scheme and the design procedure to adapt the circuit to particular needs are presented. Also experimental data obtained from a FD dc restoration circuit are presented.