LIGO Document G1300655-v1
- This poster features the design of an extremely low-noise differential transimpedance amplifier, which senses the photocurrents from two separate photodiode detectors in a Violin-mode shadow-sensor. This novel design of amplifier incorporates features which prevent %u2018noise-gain peaking%u2019 arising from large area photodiode (and cable) capacitances, and which usefully separate the DC and AC photocurrents from the photodiodes. In consequence, the differential amplifier is able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output derived from the difference in the photodiodes%u2019 two AC photocurrents. These outputs may be used for the direct calibration of the sensor%u2019s AC displacement sensitivity in terms of volts (rms)/micrometre (rms) displacement of the monitored silica suspension fibre. The results of these measurements are presented.
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