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A prototype chip for characterization of optical devices is presented based on a simple architecture. This is very useful for the characterization of Phototransistors and photodiodes and also for custom design pixels for image cameras. Phototransistors and photodiodes in a matrix of 6times4, have been used, this is, six rows by four columns. Reading is carried out in the voltage-mode which is different from other reported architecture, where current-mode is used. The pixel architecture is based on four p-channel transistors: shutter, reset, row-select and buffer integrator. The transistor called buffer-integrator in the pixel, converts the photocurrent from the photosensor into voltage. Both, the transistor buffer-integrator and a current source, form a voltage amplifier, with gain close to 32 dB. The capacitance in the integrating node was estimated from the L-Edit software extractor. Photocurrent, dark current, dynamic range and quantum efficiency, were estimated from data such as, capacitance, integrated voltage, voltage gain and time of integration. Good approximation between simulation during design and measurement on chip, was obtained which demonstrates the great powerful application of design tools.
Date of Conference: 12-14 Nov. 2008