Low noise, large area CMOS x-ray image sensor for C.T. application

Kemna, A.; Brockherde, W.; Hosticka, B.J.; Özkan, Ersin; Morales-Serrano, F.; Steadman, Roger; Vogtmeier, Gereon

doi:10.1109/icsens.2003.1279147

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…It can be seen that the input capacitance C E has to be realized as small as possible to minimize the noise. For the available application (photodetector readout), a reduced capacitance of the photodiode is presented in Kemna (2003) by using a dot diode. It must be noted that the dark current also has to be reduced to ensure maximum signal resolution.…”

Section: Results Of Noise Analysismentioning

confidence: 99%

Noise Considerations of Integrators for Current Readout Circuits

et al. 2005

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Abstract. In this paper the noise analysis of a current integrator is carried out and measures to reduce the overall noise are presented. The effects of various noise sources are investigated and their dependence on the input capacitance and on the gate area of the input transistors of the OTA used for the readout is shown. Both, input capacitance and gate area, should be kept as small as possible. Moreover, the linearity of the integrator is examined. In addition to that, the available application of such sensor readout circuit, which is a CMOS photodetector readout, is introduced. It uses an automatic gain switching, so that the dynamic range is extended.

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Section: Results Of Noise Analysismentioning

confidence: 99%

Noise Considerations of Integrators for Current Readout Circuits

et al. 2005

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“…However, not all the solutions cited above are suitable for scientific applications because they lack other fundamental characteristics like linearity or identical integration time for all the pixels. Need for post-processing of the raw digital data coming from the readout circuit is surely another disadvantage of many readout circuits proposed in literature [4,5].…”

Section: Jinst 6 C01070mentioning

confidence: 99%

Design of pixel electronics based on asynchronous self-reset approach with floating-point output representation for high dynamic range imagers

Nascetti

Valerio

2011

J. Inst.

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A readout circuit suitable for multi-channel preamplifiers for pixellated detectors, hybrid detectors or thin film on asic imagers, for applications requiring large dynamic range such as computed tomography is discussed. The circuit implements an asynchronous self-reset with residue conversion scheme combined with a floating point representation of the input current. This solution allows to reach a very high dynamic range with good linearity while ensuring a compact output format. In particular, in the present implementation the input current range extends from 50 fA up to 820 nA corresponding to a 144 dB dynamic range which is equivalent to a 24-bit code. However the proposed scheme only uses 16 output bits for the floating point representation with 12-bit constant relative resolution: 12 bits serve for the output value itself and 4 for storing the position of the transition point between integer and fractional part. In addition, an analytical study of the achievable imaging performances shows that no significant degradation of the SNR is expected for the 12-bit constant relative resolution implementation with respect to the full 24-bit resolution scheme. Finally, the main building blocks of the circuit are analyzed in detail and their characteristics are put in relationship with the overall system performances. KEYWORDS: Electronic detector readout concepts (solid-state); Front-end electronics for detector readout; Computerized Tomography (CT) and Computed Radiography (CR)

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“…This specification can be achieved in several ways. Gain switching is a commonly used technique [5]; however, it usually requires a-priori knowledge of the signal level; automatic gain switching has also been proposed [6], achieving 5-bit extension of the dynamic range. Solutions based on logarithmic amplifiers ensure large dynamic range; however, their intrinsic non-linearity makes signal processing less simple and the noise level is typically higher than with other approaches.…”

Section: Introductionmentioning

confidence: 99%

Fractional charge packet counting with constant relative resolution

Nascetti

2012

Circuit Theory & Apps

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A charge-to-digital converter concept suitable for pixel-level charge sensitive amplifiers is presented. The circuit implements a technique referred here as fractional charge packet counting, which ensures large dynamic range operation using constant integration time. By means of a particular circuit arrangement a constant number of significant bits is provided as output, thus ensuring a constant relative resolution over the entire dynamic range. A circuit implementing the concepts described above has been designed and simulated. Each block of the circuit is described in details and its characterization is presented. The circuit is capable to convert input currents in the range of 100 fA to 100 nA at 2 ksample/s with a constant resolution of 10 bit without the need of gain switching. Copyright (C) 2010 John Wiley & Sons, Ltd

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Low noise, large area CMOS x-ray image sensor for C.T. application

Cited by 7 publications

References 4 publications

Noise Considerations of Integrators for Current Readout Circuits

Noise Considerations of Integrators for Current Readout Circuits

Design of pixel electronics based on asynchronous self-reset approach with floating-point output representation for high dynamic range imagers

Fractional charge packet counting with constant relative resolution

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