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Modélisation, simulation des sources de bruit dans les capteurs d’images à pixels actifs, étude et conception d’un amplificateur opérationnel faible bruit compatible avec les APS

Abstract : This work focuses on the study and improvement of the noise performance of active pixel sensors (APS), under low illumination, and made in CMOS technology. The first part is devoted to the study and modeling of the noise sources associated with the photosensitive element and the MOS transistors integrated next to the pixels. We have developed an analytical method for calculating the power spectral density (PSD) of the LF noise (RTS noise and 1/f noise) of MOSFETs as a function of technological, geometrical and electrical parameters. The model established is based on the process of capture/emission of free charge carriers in the channel by oxide traps in the vicinity of the Si/SiO2 interface. Also, a noise PSD measurement has been established. This study allows us to define design rules for in-pixel transistors with optimal noise. In the second part, we presented a practical and efficient method to simulate the noise behavior of APS sensors directly in the time domain. This technique is fully compatible with the PSPICE simulator, which makes it easy to simulate transient circuit noise. Also, we have determined analytical expressions of the total noise variance at the output of the active pixel. The study developed in this section shows that the noise variance depends strongly on the technological and electrical parameters of the pixel and its associated transistors. We have studied the effect of the polarization and geometry of the transistors in the readout circuit. The effect of the charge capacitance was also discussed. The comparison between the results of the analytical study and those obtained by the PSPICE simulation shows that there is a good agreement between the two results. The last part of this work is devoted to the study and design of a transconductance operational amplifier (OTA) with differential output. This OTA is likely to be integrated in the acquisition chain of an APS sensor. The different stages of this amplifier have been developed. This study has shown that the noise generated by the differential input stage can be further reduced by optimizing the dimensions of the components used.
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  • HAL Id : tel-02429880, version 1

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Hassan Belahrach. Modélisation, simulation des sources de bruit dans les capteurs d’images à pixels actifs, étude et conception d’un amplificateur opérationnel faible bruit compatible avec les APS. Sciences de l'ingénieur [physics]. Université Cadi Ayyad Marrakech (Maroc), 2001. Français. ⟨tel-02429880⟩

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