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20 September 2002 Optical negative resistance detector with LBT structure
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On replacing the npn bipolar transistor by a npn phototransistor in the Lambda Bipolar transistor (LBT), we can get a novel optoelectronic negative resistance detector -- photo-Lambda bipolar transistor (PLBT). In this paper, the photo-negative resistance characteristic of this device has been demonstrated by PSPICE simulation and by a fabricated experimental device. It is shown that PLBT is not only a conventional optical detector but also a basic element in the photo-induced oscillators and in the photo-controlled frequency modulator. A wide variety of application for PLBT can be expected. PLBT is composed of a npn phototransistor as main device and a n-channel enhancement-mode MOSFET as a feed back device which connected in parallel across the base and collector terminals of phototransistor. As the VCE of photo-transistor (as same as VGS of MOSFET) is in excess of threshold voltage VT of MOSFET, then the MOSFET turns on and its drain current Id will shunt the photo-base current Iphb and the collector photocurrent Iph will decrease. The photo-negative resistance characteristic of PLBT will arise. The expressions of Iph and negative resistance RN have been derived from the physical model of PLBT. The simulation results of PSPICE are in agreement with measured data of the experimental PLBT device.
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Weilian Guo, Yunguang Zheng, Shurong Li, Luhong Mao, and Zhenkun Wang "Optical negative resistance detector with LBT structure", Proc. SPIE 4919, Advanced Materials and Devices for Sensing and Imaging, (20 September 2002);

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