The photodiodes are integrally formed on {HEAD ~ a substrate} in {TAIL ~ close enough proximity} so that the first and second photodiodes experience substantially the same environment 
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The photodiodes are integrally formed on { HEAD ~ a substrate } in { TAIL ~ close enough proximity } so that the first and second photodiodes experience substantially the same environment
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH