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Pin diode radiation detection

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Newbie level 2
Sep 24, 2007
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qse773 radiation

Hi everyone,
This is my first post for this forum, nice to join interesting stuff like this forum.
I am interested build radiation detection using pin diode and I found circuit that suit from MAXIM application notes (h**p:// that using pin diode to detect gamma radiation. I try to build the PCB and test the circuit but I could not detect any signal radiation at all

Anyone ever the the same or similiar circuit, please advise. I try using pin diode as application notes suggest, QSE773 from fairchild.

Looking for the help from everybody


It's possible the case of the diode is absorbing the dose before it reaches the silicon. You need a large area diode, perfect size is something like 300mm².

Also, the opamp or fet preamlifier must be very low noise and have similar coupling capacitance.

Here is a link to some articles on this very experiment. Let us know how it went.

**broken link removed**
**broken link removed**

Dear Freddybaby,
Many Thanks for the response. I am interested with this.
Can you suggest me the model of the pin diode that will work better for this application?

It the application circuit from Maxim in the case the coupling capacitor = 4.7pf, while the pin diode QSE773 = 20 pf. Do you think because of this different capacitance, then the circuit won't be detect anything ?


Hi Freddy&Fayes

I thinks the JFET OpAmp have low noise and suit for the application. Yes, Indeed the circuit, original have coupling capacitanse 4.7pf. I would test with higer capacitance as Freddy recommended. As from datasheet QSE477, junction capacitance about 20 pf.

Do you have better cirucuit for the application ?

Thank you all

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