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Photodiode rc filter using transistor

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nacoolp

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Hi All,

I am using a photodiode SFH206K (datasheet attached with the mail). The laser light is incident on the photodiode with a frequency of 10 and 20 Hz. Can you suggest me proper value of the RC filter given in the circuit attached with the mail. I tried with R7 = 220K and C55 = 100nF but none of the lights are detected and if I neglect the filter and nullify all the components except R7, it detects all the lights in the photodiode's sensitiity spectrum.

Thanks in advance

Nakul
 

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This is not the best way to detect laser light.

The detector is clear 400 ~1100nm so daylight and other sources of light will be detected on high gain..

The transistor gain can be high but not precise.

It depends what you are trying to do... Make use of parts on hand or design a proper laser switch.?

Common designs use transimpedance amplifiers out of Op Amps and IR detectors with daylight blocking filters ( dark plastic)

If you need help designing a simple transistor switch, start here

Increasing 100K controls the diode gain converting current to voltage but also lowers frequency response.
Collector to emitter ratios control DC gain 10:1 here. choose Beta of transistor >> base/emitter resistor ( I choose 100.)
 
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