In another circuit one of either the anodes or cathodes of each diode is common and the other is input into {HEAD ~ the inverting terminal} of {TAIL ~ a separate operational amplifier} 
of
In another circuit one of either the anodes or cathodes of each diode is common and the other is input into { HEAD ~ the inverting terminal } of { TAIL ~ a separate operational amplifier }
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 REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL