A resistor R between terminal 72 and {HEAD ~ output terminal} 78 of {TAIL ~ op amp} 68 and a resistor between terminal 74 and output terminal 80 of op amp 70 provide negative feedback for the op amps 
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A resistor R between terminal 72 and { HEAD ~ output terminal } 78 of { TAIL ~ op amp } 68 and a resistor between terminal 74 and output terminal 80 of op amp 70 provide negative feedback for the op amps
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL 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