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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Photodiodes in photovoltaic mode, speed considerations.
References: <3DACB831.F814C3D6@webaccess.net> <3DAD0481.A4004E95@NOSPAM.univ-lille1.fr> <3DAD0A0A.1F7BF2DD@webaccess.net> <email@example.com> <3DAD665D.41787E1A@webaccess.net> <firstname.lastname@example.org> <3DAD8181.24BD1A8B@webaccess.net> <email@example.com>
Date: Thu, 17 Oct 2002 00:05:07 GMT
NNTP-Posting-Date: Wed, 16 Oct 2002 17:05:07 PDT
Tony Williams wrote:
> In article <3DAD8181.24BD1A8B@webaccess.net>,
> Chuck Simmons wrote:
> > Tony Williams wrote:
> > > The simplest model (for small signals that do not
> > > induce significant diode conduction) is then of a
> > > current source (the photocurrent), in parallel with
> > > the shunt-C and the load resistor.
> > I'll try it. I think it will work.
> I've just gone through some PIN diode data sheets,
> expecting 10-90% Tr/Tf to be around the 2.2RC region.
> It only partly works, and there are some unexpected
> high anomolies. Not sure why.... maybe because the
> illumination level is making the diode conduct, or
> maybe because these data sheets (Siemens) apparently
> only quote the junction-C, without package C-stray.
I found I couldn't get at the diode directly. They have a smaller shunt
resistor than I expected. I suppose that makes sense because the diode
die sits about 2mm behind a laser die. The power out of the back end of
a laser is pretty high. I tried back flooding through the optics with a
pulsed LED without much hope. It's doubtful that as much as 5% of the
LED light makes it. I'll try pulsing the lasers tomorrow at about 50%
over threshold and hope I don't blow one. It's a new unit that we have
never used before so we know nothing about the internal sensors except
that one laser has a monitor diode with cathode common to the laser.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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