Two operational amplifiers 68 and 70 form part of circuit 50 with {TAIL ~ inverting terminal} 72 of op amp 68 common with {HEAD ~ anode} 54 of photodiode 52 
Two operational amplifiers 68 and 70 form part of circuit 50 with { TAIL ~ inverting terminal } 72 of op amp 68 common with { HEAD ~ anode } 54 of photodiode 52
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH