An amplifying circuit amplifies and outputs {TAIL ~ voltage difference} between {HEAD ~ first external input voltage} and voltage corresponding to second external input voltage 
An amplifying circuit amplifies and outputs { TAIL ~ voltage difference } between { HEAD ~ first external input voltage } and voltage corresponding to second external input voltage
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH