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Entry  Thu Aug 20 01:35:01 2015, Koji, Electronics, General, OMC DCPD in-vacuum electronics chain test OMC_DCPD_Chain.pdfOMC_DCPD_Transimpedance.pdf
    Reply  Wed Aug 26 11:31:33 2015, Koji, Electronics, General, OMC DCPD in-vacuum electronics chain test OMC_DCPD_OutputNoise.pdf
Message ID: 235     Entry time: Thu Aug 20 01:35:01 2015     Reply to this: 236
Author: Koji 
Type: Electronics 
Category: General 
Subject: OMC DCPD in-vacuum electronics chain test 

We wanted to know the  transimpedance of the OMC DCPD at high frequency (1M~10M).
For this purpose, the OMC DCPD chain was built at the 40m. The measurement setup is shown in Attachment 1.

- As the preamp box has the differential output (pin1 and pin6 of the last DB9), pomona clips were used to measure the transfer functions for the pos and neg outputs individually.

- In order to calibrate the measurements into transimpedances, New Focus 1611 is used. The output of this PD is AC coupled below 30kHz.
This cutoff was calibrated using another broadband PD (Thorlabs PDA255 ~50MHz).

Result: Attachment 2
- Up to 1MHz, the transimpedance matched well with the expected AF transfer function. At 1MHz the transimpedance is 400.

- Above 1MHz, sharp cut off at 3MHz was found. This is consistent with the openloop TF of LT1128.


Attachment 1: OMC_DCPD_Chain.pdf  46 kB  Uploaded Thu Aug 20 09:16:22 2015  | Hide | Hide all
Attachment 2: OMC_DCPD_Transimpedance.pdf  61 kB  Uploaded Thu Aug 20 09:16:35 2015  | Hide | Hide all
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