| 摘要 |
A photosensing pixel element comprises a bipolar phototransistor used as both an integrating photosensor and a select device. The phototransistor is a vertical structure, having as its collector a first doped region of a first conductivity type disposed in a semiconductor substrate or well structure. The base terminal of the bipolar phototransistor comprises a doped region of a second conductivity type disposed within the first doped region and is utilized as the select node for the pixel. Conventional field oxide regions may be employed to isolate the base regions of adjoining phototransistors. A polysilicon line doped to the first conductivity type is disposed over the surface of the semiconductor substrate and is insulated therefrom except in regions where it is in contact with the doped region of a second conductivity type to form an epitaxial emitter for the phototransistor. The polysilicon line also forms the emitter contact for the phototransistor. A plurality of integrating photosensors may be placed in an array of rows and columns, wherein the bases of all bipolar phototransistors in a row are capacitively coupled together to a common row-select line, and the emitters of all bipolar phototransistors in a column are integral with a column sense line. The input of a sense amplifier is connected to the sense line of each column of integrating photosensors. An integrating sense amplifier according to the present invention includes an amplifying element having an inverting input connected to the sense line. A capacitor, preferably a varactor, is also connected between the inverting input and output of the amplifying element. An exponential feedback element may be provided in the sense amplifiers for signal compression at high light levels. The outputs of the sense amplifiers are connected to sample/hold circuits. The rows of the array are selected one at a time and the outputs of the sample/hold circuits for each row are scanned out of the array while the pixel data for the next row are sampled.
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