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