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Noise I Abigail Firme Introduction Characterization 1 Frequency Amplitude Mechanism responsible Types of Noise Interference Random Noise Johnson Noise Shot Noise Flicker Noise Johnson Noise Thermal Noise is caused by voltage generated by moving charge carriers ID: 762423
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Noise I Abigail Firme
Introduction Characterization [1] Frequency Amplitude Mechanism responsible Types of NoiseInterferenceRandom NoiseJohnson NoiseShot NoiseFlicker Noise
Johnson Noise “Thermal Noise” is caused by voltage generated by moving charge carriers. Also characterized as white noise with flat frequency spectrum. Sensitivity Limiting Factor. [1] [4] [5]
Shot Noise Electronic Shot Noise rms Current Fluctuations [1] Usually small compared to Johnson Noise and 1/f noise. Optical Shot Noise Fluctuations in number of photoelectrons Probability follows Poisson distribution. [2] [6] [1]
Noise Reduction Johnson Noise Three options for noise reduction: Resistance, Temperature, and Bandwidth. Ideal resistance in superconductors: R = 0. Resistance or impedance reduction limited by equipment components. Temperature reduction is common when studying samples at low temperatures, but is not commercially feasible. Bandwidth reduction is most common. Averaging or filtering. Shot NoiseTwo options for noise reduction: Current and Bandwidth. Reduction of current through the system corresponding to high optical signal input. Bandwidth reduction
Photomultipliers Collect photons from low light and amplify the signal. Kept at low temperatures to eliminate thermal noise. Remaining noise is shot noise. [3] Background Light Signal Light [2]
Amplifier Noise Amplifies total signal plus noise, but introduce additional noise in the process. [1] Low noise amplifiers choose optimal I c Based on i n Based on R s [1] [7]
References [1] Paul Horowitz, Winfield Hill, ‘The Art of Electronics’ , 1989, p. 286-290. [2] Robert L. McClain, John C. Wright, ‘Description of the Role of Shot Noise in Spectroscopic Absorption and Emission Measurements with Photodiode and Photomultiplier Tube Detectors: Information for an Instrumental Analysis Course’, American Chemical Society, 2014, p. 1455 – 1457.[3] Hamastu Photonics K. K., ‘Photomultiplier Tubes: Basics and Applications’, Third Edition, 2007, p. 129 – 133.[4] http://www.bitlanders.com/blogs/free-electrons-in-metals-and-related-terms/253854 [5] http://www.rfcafe.com/references/electrical/noise-power.htm [6] https://www.codrey.com/dc-circuits/conventional-current-vs-electron-current/[7] https://gpio.com/2017/02/16/what-is-a-low-noise-amplifier/