[Laser] Photodiodes in series

[John Matz]

It seems like putting photodetectors in series would be a pretty
unpredictable configuration, unless they were being used in a photovoltaic
mode or some such.  I usually think of photodetectors as operating as
current sources, having some dark current, and producing some current from
light photons striking their surface.  In which case, I would consider
connecting them in parallel, where their dark currents simply add, and their
internal capacitances simply add, their active areas just add, but their
responsivity in mA per mW is unchanged.  You just get a bigger detector and
lose a little sensitivity and bandwidth.  But putting them in series ... I
don't know ... Csh are in series, Rsh are in series, which doesn't change
the bandwidth much, unless the load is much less than Rsh.  Yves may have
the best available analysis, having tried it.
John Matz KB9II
----- Original Message -----
From: Zilvinas Atkociunas <zilvinas at augma.lt>
To: Free Space LASER Communications <laser at mailman.qth.net>
Sent: Wednesday, January 24, 2007 2:47 PM
Subject: [Laser] Photodiodes in series


> Hi all,
>
> Does anybody know how connecting several pin photodiodes in series would
> affect performance of receiving system (bandwidth, sensitivity, noise) ?
>
> 73 de ly2ss
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