LIGO Document E1200814-x0

DCN for schematic changes to aLIGO ISC QPD Transimpedance Amplifier

Document #:
LIGO-E1200814-x0
Document type:
E - Engineering documents
Abstract:
A detailed record of changes to schematic from revision v3 to v4
Files in Document:
None
Authors:
Keywords:
DCN ISC QPD
Notes and Changes:
1. The existing aLIGO boards are manufactured using v2 PCBs. Revision v4 includes a cleanup of several CAD typos associated with the v2 PCB, and as such should be used to order future boards.
2. A jumper was added (P1) to the output of the noise amplifier to facilitate testing and evaluation of the circuit in the absence of a noise cancellation circuit
3. All the I to V stages were previously implemented with AD8675 operational amplifiers. These amplifiers were found to be easily damaged resulting in subtle and not so subtle changes in bandwidth and noise characteristics. All AD8675 amplifiers used in U4 and U6 stages, have been changed to OP-27 operational amplifiers. The noise was checked per the test procedure, and no negative consequences were noted.
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