Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1997-09-17
1999-08-03
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
250214R, 438 66, 438 79, H01L 2100
Patent
active
059328738
ABSTRACT:
A capacitor coupled bipolar phototransistor having an integrated electronic shutter for reducing the overflow and blooming problems associated with the imaging of strong images. Overflow control and an anti-blooming mechanism are obtained by use of a second emitter (the "shutter") which is used to remove excess image generated charge. This prevents the base-emitter junction potential from becoming forward biased during image integration when the phototransistor is exposed to a strong image. The shutter is biased slightly lower than the first emitter of the phototransistor so that the base-shutter junction is forward biased sooner than the base-emitter junction when the imaging element is exposed to a strong image. The overflow current of the generated holes is then drained to the shutter, rather than into the emitter where it would produce noise on the column sense line.
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Bergemont Albert
Chi Min-hwa
Haggag Hosam
Mead Carver
Foveon, Inc.
Le Que T.
Lee John R.
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