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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: photodetector circuit, high speed with good ambient light rejection
Date: Thu, 28 Nov 2002 17:57:27 GMT
NNTP-Posting-Date: Thu, 28 Nov 2002 12:57:27 EST
"Dr C.I. Swift" wrote:
> Need to make such a circuit good for up to 90MHz. will have a considerable
> DC light component so want too reject this.
> Is it possible to reverse bias the photodiode, running it to ground via an
> inductor in series with the resistor? The idea being the ac component will
> seee a higher impedence and therefore produce a higher voltage.
> Or should I stick to the transimpedence amplifier with a feedback resistor
> small enough so that the system does not saturate and then just ac couple
> the signal to further amplification stages.
> Any help or suggestions would be greatfully recieved
> Many thanks
If you are going ot include an inductor, put it in the feedback of the
transimpedance amplifier (with a parallel resistor to set the high
frequency gain). Also, it may be worth while to invest in a narrow
band optical filter in front of the diode, to limit the ambient light
to only the wavelengths near your signal. You can also increase the
bandwidth of the diode amplifier by reverse biasing the diode.
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