Publication: Design digital-to-analog converter and voltage-to-current converter in pixel readout circuit for x-ray images
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Date
2012-06-01
Authors
Azmi, Nur Asma Hidayah
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Abstract
Image sensors have gained a lot of interest lately in many applications such as cameras, television, cellular phones, and other devices. These applications are predominantly designed by CMOS transistors due to low cost and good signal processing capability. For x-ray images, sequential series of study has been done to obtain clear image of an inner body structures. X-ray images can be varies depend on radiation intensity that passes through the body and recorded on radiographic film. Digital pixel sensor is used to read the data image because it can reduces the noise introduced by the commutations of the analog circuit. In each pixel blocks of x-ray image, it is consists by a photodetector and A/D converter which called sigma delta converter. The circuit of converter constitute of integrator, comparator,1-bit digital-to-analog converter (DAC). The research is to design 1-bit DAC so that it is compatible to use them along with integrator and comparator in sigma delta converter with low noise. Voltage to current converter (V/I) is also implemented in the design. It used to convert the voltage output to current output reading. At the end of this project, it is concluded that DAC can obtain offset error and gain error by 290.34mLSB and 0.286LSB. The power consumption produced for the whole circuit is around 0.0302nW. This project is done using Cadence Software in 0.18um CMOS technology.