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Proceedings Paper

Negative resistance characteristic in optoelectronic composite device
Author(s): M. Satyam; Krishnaswamy Ramkumar; M. Anadan
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Paper Abstract

This paper describes the nagative resistance characteristic exhibited by a composite optoelectronic device consisting of a liquid crystal display and a phtoconductor. This characteristic is suitable for memory devices optical pattern generators and special oscillator circuits. Devices like SCR UJT Tunnel diode are known to exhibit negative resistance characteristics and hence electrical bistability (1) A liquid crystal display (LCD) (2) in series with a photoconductor (PC) is known to exhibit optical bistability (3 4). The electrical characteristics of this or any other combination of these devices has to our knowledge not been reported so far. It is found that a parallel combination of these devices exhibits a negative resistance characteristic which is described below. Fig. I Structure of the LCD-LDR optoelectronic device. 274 transparent LCD is connected to a PC in parallel and placed such that the light passing through the LCD falls directly on the PC. The transmmission characteriastic of the LCD is given graphically as shown in Fig. 2. To a first approximation the transmittance T of the LCD can be expressed as T Tmax when A V VB T Tmax - K(V - VB) when VB I '''' T Tmin when VC V VD where I Initially the transmittance of the LCD is Tmax and hence the resistance of the PC is Rein which may be approximately written as Fig. 2 : Transmission composite characteristics of the

Paper Details

Date Published: 16 December 1992
PDF: 4 pages
Proc. SPIE 1622, Emerging Optoelectronic Technologies, (16 December 1992); doi: 10.1117/12.636960
Show Author Affiliations
M. Satyam, Indian Institute of Science (India)
Krishnaswamy Ramkumar, Indian Institute of Science (India)
M. Anadan, Indian Institute of Science (India)

Published in SPIE Proceedings Vol. 1622:
Emerging Optoelectronic Technologies
Krishna Shenai; Ananth Selvarajan; C. Kumar N. Patel; C. N. R. Rao; B. S. Sonde; Vijai K. Tripathi, Editor(s)

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