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Noiseless AC Coupling for balanced detection using a common adjustable current sink

Invention Reference Number


Technology Summary

Balanced detection is a method of light detection in which classical noise common to two detectors is removed by subtracting the individual detector signals from one another. This is useful for very sensitive measurements such as beam positioning measurements, laser absorption spectroscopy, and optical homodyne detection. In some applications, the signal to be detected and amplified is an AC signal, and the nature of the amplification process requires the DC signal to be eliminated while still meeting amplification and bandwidth performance for the AC signals. This invention disclosure details a method of AC coupling a balanced detector that preserves photodiode bandwidth in a biased configuration, allows optimal transimpedance amplifier performance, retains DC signal measurement capability, and does not introduce additional noise into the balanced detection signal.


Brian P. Williams
Computational Sciences & Engineering Division

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