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Proceedings Paper

Expanding the bandwidth of low level photo-electric amplifier using continuous equal-potential shielding
Author(s): Kai Xie; Bin Sun; Xueyou Shi; Anfeng Huang; Ruoyao Xi
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Paper Abstract

For the low level current preamplifier circuits in photo-electric detection, the bandwidth and the low noise characteristics are usually contradictory, because the bandwidth is limited by the high value resistor and its inevitable parasitic capacitances, which together exhibit low-pass characteristics. To expand the bandwidth of low level current amplifier, a novel method is proposed by using continuous equal-potential shielding to eliminate the parasitic capacitances and expand the bandwidth. The shielded resistor contains three layers: the center is high value resistance strip; the top and bottom layers are high conductivity shielding films with same path to center strip. The surrounding electric field energy could be provided by shielding structure instead by high value resistor itself, so the parasitic capacitances would be greatly reduced. In this paper, the principle and the structure of the equal potential shielding are presented, and the possible results are predicted by finite element simulation. The simulation was conducted by the ultra-low current preamplifier with a trans-impedance gain of 50 GΩ. The results indicated that the parasitic capacitances reduced from 1.36×10-2pF to 1.18×10-3pF, meanwhile the bandwidth was expanded from 234.1 Hz to 2.43 kHz with more than 10 times of increase; the rise time decreased from 1.53ms to 0.085ms. The advantage of this method is that the bandwidth could be expanded without extra compensation; meanwhile the shielding layers improve the noise immunity. This method is suitable for the demand of rapid response to low level current in photo-electric detection field, such as scanning tunneling microscopy and laser radar.

Paper Details

Date Published: 8 March 2017
PDF: 5 pages
Proc. SPIE 10255, Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016, 102553Y (8 March 2017); doi: 10.1117/12.2268057
Show Author Affiliations
Kai Xie, Xidian Univ. (China)
Bin Sun, Xidian Univ. (China)
Xueyou Shi, Xidian Univ. (China)
Anfeng Huang, Xidian Univ. (China)
Ruoyao Xi, Xidian Univ. (China)

Published in SPIE Proceedings Vol. 10255:
Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016
Yueguang Lv; Jialing Le; Hesheng Chen; Jianyu Wang; Jianda Shao, Editor(s)

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