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Entry  Thu Nov 11 02:17:27 2010, Kevin, Update, Electronics, REFL11 Photodiode Not Working 
    Reply  Thu Nov 11 07:26:03 2010, Alberto, Update, Electronics, REFL11 Photodiode Not Working 
Message ID: 3890     Entry time: Thu Nov 11 02:17:27 2010     Reply to this: 3893
Author: Kevin 
Type: Update 
Category: Electronics 
Subject: REFL11 Photodiode Not Working 

[Koji and Kevin]

I was trying to characterize the REFL11 photodiode by shining a flashlight on the photodiode and measuring the DC voltage with an oscilloscope and the RF voltage with a spectrum analyzer. At first, I had the photodiode voltage supplied incorrectly with 15V between the +15 and -15 terminals. After correcting this error, and checking that the power was supplied correctly to the board, no voltage could be seen when light was incident on the photodiode.

We looked at the REFL55 photodiode and could see ~200 mV of DC voltage when shining a light on it but could not see any signal at 55 MHz. If the value of 50 ohm DC transimpedance is correct, this should be enough to see an RF signal. Tomorrow, we will look into fixing the REFL11 photodiode.

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