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Entry  Mon Sep 9 15:00:19 2013, Evan, DailyProgress, ISS, Beefier ISS loop ctn_rin_clopen.pdf
    Reply  Wed Sep 11 00:07:04 2013, Evan, DailyProgress, ISS, Beefier ISS loop 
Message ID: 1333     Entry time: Wed Sep 11 00:07:04 2013     In reply to: 1330
Author: Evan 
Type: DailyProgress 
Category: ISS 
Subject: Beefier ISS loop 

Quote:

I made a quick inverting op-amp integrator which kicks in at 860 Hz at has gain 10 at infinity. The feedback is a 5.6 kΩ resistor in series with a 33 nF capacitor. On the inverting input there is a 560 Ω resistor.

I put this after the SR560 with gain set to 100 and bandwidth set to 30 kHz. It seems like this gives good RIN suppression.

I changed the values so that the feedback is 13 kΩ in series with 1.2 nF, and the inverting input is 1.3 kΩ. This puts the zero at 10 kHz.

I duplicated this with a second OP27 on the same circuit board, so now there is an integrator for each cavity.

Last night the best results seemed to be achieved with the SR560s set to G = 100 with a pole at 10 kHz.

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