COMPENSATION CIRCUIT FOR NULLIFYING DIFFERENTIAL OFFSET VOLTAGE AND REGULATING COMMON MODE VOLTAGE OF DIFFERENTIAL SIGNALS

摘要

COMPENSATION CIRCUIT FOR NULLIFYING DIFFERENTIALOFFSET VOLTAGE AND REGULATING COMMON MODE VOLTAGEOF DIFFERENTIAL SIGNALSAbstract of the DisclosureAn apparatus for nullifying the differential outputoffset voltage between the outputs of a differentialamplifier and for setting the DC levels of the outputs to aknown reference voltage includes a circuit which cross-couples the opposing AC output signals to obtain only the DCcomponents of each signal. The apparatus further includes afirst operational amplifier to generate a compensationvoltage from the DC components of the outputs of thedifferential amplifier proportional to the amount of offsetbetween the DC components of the outputs of thedifferential amplifier. The compensation voltage is fedback to the offset control inputs of the differentialamplifier to reduce the differential offset voltage tosubstantially zero volts. The apparatus further includes adual voltage divider network having a second operationalamplifier that supplies a variable reference voltage to oneterminal of each leg of the voltage divider network. Theoutputs of the differential amplifier are each provided to arespective other terminal of the dual voltage dividernetwork. The second operational amplifier has a referencevoltage on one of its inputs. A signal responsive to thecommon mode output voltage from the differential amplifieris provided to the other input. The second operationalamplifier provides an output voltage that is responsive tothe common mode voltage output from the differentialamplifier. The output voltage from the second operationalamplifier provided to the terminals of the dual voltagedivider network varies such that the voltage outputs fromthe voltage divider network have a common mode voltagesubstantially equal to the reference voltage.ARCHA.C28JTS-6188890803/1