Tuesday, November 25, 2008

Fairchild Imaging Toys with 4T Pixels

Fairchild Imaging presented a 4T pixel paper on SPIE Astronomical Telescopes and Instrumentation Conference, 23-28 June 2008, Marseille, France. It shows quite a conventional 6.5um pixel made in 0.18um process. What really sets it apart is a very low full well - only 1.5Ke at most.

: As mentioned in comments, probably the full well is limited by column amplifier in high-gain mode. The pixel's native full well is probably higher, albeit the paper does not give an explicit number.
Update #2: Two sentences removed, as said in comments.


  1. Well, Boyd ain't no dummy so maybe rethink that statement. Say, what would happen if you really cranked the conversion gain up? (haven't read the paper) and then read the sensor multiple times during an exposure to get your dynamic range? Would make your ktc/FPN cancellation easier (larger signal, less finesse on the downstream cct's)? That's just one way to do it.

  2. I just read it quickly. The 1.5Ke is the result in high gain mode (700 uV/e)(gain in column). I guess it is only used to measure the ultimate pixel noise performance... The pixel itself has 30Ke or so.

  3. As far as I can see 30Ke number relates to the first phase of the work, while the paper describes the second phase. But you are probably right that the full well is limited by their column amplifier in high-gain mode. Honestly, this is the first time I see such a way to report full well. And they do not tell what is the pixel's "native" full well.

    I'm adding this correction to my post.

  4. I hope you remove the "ashamed" part of your post. It was an error in your understanding and not a professional thing to say. It diminishes the fine blog you have created.
    Also, it is important to the community that people are able to publish on work in progress, including success and failure. It is how we all learn together.
    -Eric Fossum

  5. OK, I'm sorry. I removed this statement.


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