The University of Southampton

Monolithic Active Pixel Arrays

Date:
2001-2006
Themes:
Silicon Based Photonics, Materials & Technology

A visible wavelength linear photosensor featuring a pixel size of 3 mm has been designed for fabrication using commercial 0.25 mm 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 71V swing for improved power supply noise rejection. The readout circuitry is designed for 12 bit accuracy at frame rates of up to 6.25 kHz. 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 66.3 for a full well capacity of 255,000, giving a dynamic range of 71.7 dB.

Primary investigators

Secondary investigator

  • Quentin Morrissey

Partner

  • N.R. Waltham, Rutherford Appleton

Associated research groups

  • Nano Research Group
  • Electronic Systems and Devices Group
  • Electronics and Electrical Engineering
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