Authors : Qamrul Huda , Fouzia Ferdous , Jesmin Farzana Khan and Khadiza Tahera
Abstract: LED is an opt-electronic device which is generally used as an optical source and converts electrical energy into optical source. We have to use LED as a photodetector. Photodetector behaves like a current source such that under reverse bias condition and we get photocurrent. Photocurrent varies with wavelength of light i.e. color of light. Here we detect the color of light in the visible range of frequency spectrum by observing this photocurrent. We design a circuit that can be used to detect four color of light. We represent the detected light in a suitable binary form by using a logic circuit. But the magnitude of the photocurrent is normally too small to interface directly to a logic gate. This condition indicates that an amplifier is needed between reverse biased LED and logic circuit.
Qamrul Huda , Fouzia Ferdous , Jesmin Farzana Khan and Khadiza Tahera , 2005. Design of a Detector Circuit in the Visible Region by Using LED . Asian Journal of Information Technology, 4: 562-564.