Design of a 3 μm pixel linear CMOS sensor for earth observation

Q. R. Morrissey*, N. R. Waltham, R. Turchetta, M. J. French, D. M. Bagnall, B. M. Al-Hashimi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

A visible wavelength linear photosensor featuring a pixel size of 3μm has been designed for fabrication using commercial 0.25μm CMOS technology. For the photo-sensing element, the design uses a special "deep N-well" in P-epi diode offered by the foundry for imaging devices. Pixel reset is via an adjacent p-FET, thus allowing high reset voltages for a wide pixel voltage swing. The pixel voltage is buffered using a voltage-follower op-amp and a sampling scheme is used to allow correlated double sampling (CDS) for removal of reset noise. Reset and signal levels are buffered through a 16:1 multiplexer to a switched capacitor amplifier which performs the CDS function. Incorporated in the CDS circuit is a programmable gain of 1-8 for increased signal-to-noise ratio at low signal levels. Data output is via 4 analogue output drivers for off-chip conversion. Each driver supplies a differential output voltage with a ±1V swing for improved power supply noise rejection. The readout circuitry is designed for 12 bit accuracy at frame rates of up to 6.25kHz. This gives a peak data rate at each output driver of 10M samples/s. The device will operate on a 3.3V supply and will dissipate approximately 950mW. Simulations indicate an equivalent noise charge at the pixel of 66.3e- for a full well capacity of 255,000e-, giving a dynamic range of 71.7dB.

Original languageEnglish
Pages (from-to)350-357
Number of pages8
JournalNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment
Volume512
Issue number1-2
DOIs
Publication statusPublished - 11 Oct 2003
Externally publishedYes

Keywords

  • linear photosensor
  • CMOS
  • photodiode
  • Earth observation

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