first voltage source connected across each of {TAIL ~ said photodiodes}, biasing each of {HEAD ~ said photodiodes}; and 
first voltage source connected across each of { TAIL ~ said photodiodes } , biasing each of { HEAD ~ said photodiodes } ; and
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH