• 전기의세계
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• v.11
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• pp.8-13
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• 1963

Solid state nuclear radiation detector에 사용되는 transistor에 의한 저잡음 charge sensitive preamplifier의 설계방식과 이에 대한 실측결과에 관하여 기술하였다. 먼저 transistor noise의 제원인을 분석하고 이 잡음들을 최소로 하기 위하여 이에 관련된 각 parameter에 대하여 이론 및 실험적으로 고찰하였다. 지금까지 알려진 진공관식 증폭기의 최소잡음은 등가전자수로 표시하면 약 250전자 정도이고 그 transistor증폭기에 있어서는 약 1,000전자 정도이었으나 본 설계방식에 의하여 제작된 transistor증폭기에서는 detector를 포함한 전 input capacitance가 약 100PF일때 약 400전자의 양호한 저잡음특성을 보이고 있으며 linearity 및 stability도 매우 좋은 결과를 보이고 있다. 여기에 사용된 cascode회로 자체는 이미 오래 전부터 알려져 있었지만 잡음을 최소로 하기 위한 설계방법은 지금껏 알려지지 않고 있으므로 본 논문에서는 전치증복기의 소요이득에서 잡음을 최소로 할 수 있는 설계방식을 확립하여 이 방식에 의한 실측결과는 종래의 transistor를 사용한 것보다 가장 좋았다.

• International journal of advanced smart convergence
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• v.1 no.1
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• pp.61-64
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• 2012

The ultraviolet and visible light responsive properties of the amorphous indium gallium zinc oxide thin film transistor have been investigated. Amorphous indium gallium zinc oxide (a-IGZO) thin film transistor operate in the enhancement mode with saturation mobility of $6.99cm^2/Vs$, threshold voltage of 13.5 V, subthreshold slope of 1.58 V/dec and an on/off current ratio of $2.45{\times}10^8$. The transistor was subsequently characterized in respect of visible light and UV illuminations in order to investigate its potential for possible use as a detector. The performance of the transistor is indicates a high-photosensitivity in the off-state with a ratio of photocurrent to dark current of $5.74{\times}10^2$. The obtained results reveal that the amorphous indium gallium zinc oxide thin film transistor can be used to fabricate UV photodetector operating in the 366 nm.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.1
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• pp.7-15
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• 2007

This study aim to investigate image characteristics due to focus-grid and head phantom decentering from the armorphos silicon thin film transistor detector the fixed focus-grid is applied, wish to propose right use method of digital medical equipment. Acquired image according to focus-grid and head phantom position decentering using head phantom on armorphos silicon thin film transistor detector the fixed focus-grid is applied. acquired image evaluate pixel value, histogram, plot profile, surface plot using NIB (Image J) image analysis program and compared decentering image with standard image. Mean value and standard deviation value of focus-grid lateral decentering and duplex decentering of focus-grid and head phantom decreased by ratio, consequently increase of horizontality, diagonal decentering. also, deteriorated contrast of image because frequency of high pixel value decreases fairly. according increases decentering, image distortion phenomenon was increase, by next time, pixel mean value of head phantom decentering was no big change but horizontality, diagonal, mean value and standard deviation value of pixel decreased by ratio. Even if increase pixel noise of image because wide latitude and post processing ability of digital detector, radiotechnologist can not recognize. Therefore, radiotechnologist must recognize correctly the photographing factors which increases pixel noise on the grid system installation digital detector and should exam.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.395-398
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• 2002

Many research group started study to develope x-ray detector using thin film transistor from 1970. But realization of TFT based x-ray detector development was caused by progress of thin film transistor liquid crystal display(TFTLCD) device technology in 1990. The main current of TFT technology is display device. Research results expend TFT technology field from display device to sensor manufacture technology. These days many research group in the world realize various digital x-ray detector. In this study, We compare discharge erasing method to visible light erasing method in a-Se based digital x-ray detector. Visible light erasing method is known reset process in direct conversion x-ray detector. Digital x-ray detector using visible light erasing method is not adaptive for conventional x-ray device, because of its thickness. And it is not avaliable for real-time imaging for digital fluoroscopy, because of its long reset time. In this study we overcome these limitations and show new idea for real-time imaging method.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.2
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• pp.23-30
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• 2007

This study attempts to propose an appropriate method of using digital medical imaging equipments, by studying the effects of automatic exposure control(AEC), grid ratio and the change of radiography distance on the patient dose and detertor acquisition dose during the procedure of acquiring image through a digital medical imaging detector. The change of dose following the change of grid ratio's exposure and radiography distance was measured, by using an abdominal phantom organized with tissue equivalent materials in an amorphous silicon thin film transistor detecter installed with AWC. The case to use grid ratio 12 : 1, focal distance 180cm to radiography distance 110cm in AEC, the patient dose increased rather when we used grid ration 10 : 1, focal distance 110cm. When AEC was not used,the dose necessary for image acquisition decreased as the grid ratio became higher and the distance became further. but detector acquisition dose was not reduced when in applied AEC. When purchasing digiral medical imaging equipments, optional items such as AEC and grid shall be accurately selected to satisfy the use of the equipments. Radiography error made by radiation technologist and unnenessary patient dose can be reduced by selecting equipments with a radiography distance marker equipment when it did not apply AEC. These equipments can also be helpful in maintaining high imaging quality, one of the merits of digital detectors.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.359-365
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• 2023

In order to satisfy the requirements of dynamic X-ray imaging with high frame rate and low image lag, minimizing parasitic capacitance in photodiode and overlapped electrodes in pixels is critically required. This study presents duoPIX^TM dynamic X-ray imaging sensor composing of readout thin film transistor, reset thin film transistor and photodiode in a pixel. Furthermore, dynamic X-ray detector using duoPIX^TM imaging sensor was manufactured and evaluated its X-ray imaging performances such as frame rate, sensitivity, noise, MTF and image lag. duoPIX^TM dynamic X-ray detector has 150 × 150 mm² imaging area, 73 um pixel pitch, 2048 × 2048 matrix resolution(4.2M pixels) and maximum 50 frames per second. By means of comparison with conventional dynamic X-ray detector, duoPIX^TM dynamic X-ray detector showed overall better performances than conventional dynamic X-ray detector as shown in the previous study.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.11
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• pp.7-13
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• 2002

BSCT 320${\times}$240 IRFPA detector module is implemented, which is a key component in uncooled thermal imaging systems. The detector module consists of two parts, infrared sensitive pixel array and read-out integrated circuit(ROIC). The BSCT 320${\times}$240 pixels are made by laser scribe process and 10-${\mu}m$ micro-bump to satisfy 50-${\mu}m$ pitch and 95-% fill-factor. The ROIC has been designed to electrically address the pixels sequentailly and to improve signal-to-noise ratio with single transistor amplifier, HPF, tunable LPF and clamp circuit. The fabricated hybrid chip of detector and ROIC has been mounted on the TEC built-in ceramic package for more stable operation and tested for lots of electrical and optical properties. The IRFA sample has shown successful properties and met with good results of fill-factor, detectivity and responsivity.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.69-72
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• 2000

This paper describes an SRAM write driver circuit which dissipates small power. The write driver utilizes a dual sized transistor structure to reduce operating current in the write cycle. In the case of higher voltage comparing to Vcc, only one transistor is active, while in the case of low Vcc two transistors are active so as to deliver the current twice. Thus though with the high voltage operation, the power consumption is reduced with keeping the speed in a given specification. Simulation results have verified the functionality of the new circuit and write power is reduced by 7 % per bit.

• Journal of Magnetics
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• v.7 no.1
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• pp.4-8
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• 2002

The magnetoresistance (MR) and the magnetization reversal of a lateral spin-injection device based on a spin-polarized field effect transistor (spin FET) have been investigated. The device consists of a two-dimensional electron gas (2DEG) system in an InAs single quantum well (SQW) and two ferromagnetic $(Ni_{80}Fe_{20})$ contacts: all injector (source) and a detector (drain). Spin-polarized electrons are injected from the first contact and, after propagating through the InAs SQW are collected by the second contact. By engineering the shape of the permalloy contacts, we were able to observe distinct switching fields $(H_c)$ from the injector and the collector by using scanning Kerr microscopy and MR measurements. Magneto-optic Kerr effect (MOKE) hysteresis loops demonstrate that there is a range of magnetic field (20~60 Oe), at room temperature, over which the magnetization in one contact is aligned antiparallel to that in the other. The MOKE results are consistent with the variation of the magnetoresistance in the spin-injection device.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.413-419
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• 2012

A dynamic range extension technique is proposed based on a 3-transistor active pixel sensor (APS) with gate/body-tied p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector using a feedback structure. The new APS consists of a pseudo 3-transistor APS and an additional gate/body-tied PMOSFET-type photodetector, and to extend the dynamic range, an NMOSFET switch is proposed. An additional detector and an NMOSFET switch are integrated into the APS to provide negative feedback. The proposed APS and pseudo 3-transistor APS were designed and fabricated using a $0.35-{\mu}m$ 2-poly 4-metal standard complementary metal oxide semiconductor (CMOS) process. Afterwards, their optical responses were measured and characterized. Although the proposed pixel size increased in comparison with the pseudo 3-transistor APS, the proposed pixel had a significantly extended dynamic range of 98 dB compared to a pseudo 3-transistor APS, which had a dynamic range of 28 dB. We present a proposed pixel that can be switched between two operating modes depending on the transfer gate voltage. The proposed pixel can be switched between two operating modes depending on the transfer gate voltage: normal mode and WDR mode. We also present an imaging system using the proposed APS.