Phil проговорился...
http://groups.google.ru/group/sci.electron...e3f8?hl=ru&advanced photoreceiver that maintains
shot-noise-limited performance (2 dB above shot noise) from ~10 nA to
100 uA, with an honest 1 MHz bandwidth over (almost) the whole range.
Doing that down near the minimum photocurrent is a real genuine parlour
trick.
The ones uses two photodiodes wired in series (!) to get a
sub-Poissonian photocurrent to null out the primary photocurrent.
That's a trick I've never seen before, so I might have invented it. It
obviously requires some careful feedback to keep the currents in
balance, but the result is a nice linear photoreceiver with almost no
additional input capacitance.
Two photodiodes in series have the same photocurrent but *half the shot
noise*, so the cancellation current is actually quieter than the
photocurrent, without needing resistive degeneration. (I also manage to
keep all 300-kelvin resistors out of the signal path, which is key.)
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