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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>
Date: Wed, 16 Oct 2002 15:11:11 GMT
NNTP-Posting-Date: Wed, 16 Oct 2002 08:11:11 PDT
Tony Williams wrote:
> In article <3DAD665D.41787E1A@webaccess.net>,
> Chuck Simmons wrote:
> > ........................................ The question is
> > predicting the speed of the diode given inadequate data
> I think you need to know the capacitance of each
> diode.... the sum of the C-stray plus the zero-
> -bias junction capacitance. Get the figure from
> the mfr, or where they bought the diode-die from.
> Or, (worst case), measure it yourself at a max
> stimulus of about 100mV peak.
The last is a very good suggestion I think. I can try it on some
photodiodes in the dead pile (the lasers are dead). Going to the mfr is
a waste of time. Only one has given us a BOM of their optics. They seem
to have figured out which side of the business we are on and don't feel
> Junction-C is a maximum at zero-bias, maybe more
> than 5x that at a reverse-bias above 10V.
> 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.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
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