Wednesday, May 11, 2016

Soft Reset Noise Analysis

Open-source Sensors journal publishes paper "Analysis of Subthreshold Current Reset Noise in Image Sensors" by Nobukazu Teranishi. The analysis also includes a tapered reset with a feedback amplifier:


  1. "Only reset noise or RST channel noise is considered here; noises from the SF, the differential amplifier, SEL and wiring resistances are not included, because the reset noise is dominant."

    While that is interesting as an exercise, as the noise values begin to approach a few electrons, I suspect that noise contributions from SF white and 1/f, SEL, wiring resistance and ESPECIALLY the feedback amplifier become a bit more than relevant.

    Plotting noise levels down to <0.01e- using this analysis is disingenuous. It is equivalent to predicting the fuel economy of a gasoline engine automobile at velocities from 0 mph to 1000 mph and stating that:

    "Only inertia and tire friction are considered here; losses from the air friction, friction of internal engine components, friction of drivetrain are not included, because inertia and tire friction are dominant at low speeds".

  2. if you cant do CDS, the 1/f noise of source follower will kill your low noise performance.

  3. In the patent: "9,094,612 Back side illuminated global shutter image sensors with back side charge storage" there is a better description of eliminating the FD reset noise by a double reset.


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