An output of the operational amplifier is fed back to {HEAD ~ an input} of {TAIL ~ the operational amplifier} through a current varying element that varies current levels of the input of the operational amplifier to remove a level shift of an output signal of the differential amplifier 
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An output of the operational amplifier is fed back to { HEAD ~ an input } of { TAIL ~ the operational amplifier } through a current varying element that varies current levels of the input of the operational amplifier to remove a level shift of an output signal of the differential amplifier
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH