What is the difference between MOS and CMOS?

  • The Panasonic Lumix DMC-FZ1000 has, according to the specs, a MOS image sensor - while cameras usually have CMOS (or CCD, for that matter).

    Is there any difference between MOS and CMOS? Or is this a simple marketing trick?

  • TFuto

    TFuto Correct answer

    5 years ago

    MOS means Metal Oxide Semiconductor. It is a specific way of device formation on silicon wafer. See this link.

    MOS, unqualified, usually means using a single doping technique to either create n-channel (typically) or p-channel FETs (field effect transistors). When ICs are manufactured this way, the costs are reduced. The disadvantage is that a certain amount of power is consumed if the device is powered but actually not doing any useful work. n-MOS has the advantage of reduced chip area, and if the specification is true, they may be using NMOS exclusively for more pixel density.

    CMOS means complementary MOS, when both n-channel and p-channel FETs are created (and so it requires at least two doping pass in manufacturing). The effect is increased cost, but n-FET and p-FET transistors together allow for creation of static CMOS logic gates. These consume very little power when not toggling (there is static power consumption only because of some leakage current), and so these day CMOS, and consequently static logic cells are used almost exclusively in low-power applications, where battery lifetime is critical.

    That having been said, I can imagine a nice sensor circuit that uses only NMOS devices, and handles power-related issues in a separate circuit.

    Sorry but this answer is incorrect, in this regard MOS and CMOS are equivalent

    If you want to start an argument, state your facts (and make sure you know your facts right before).

    This is a good answer, but what do you mean in the last paragraph by handling power-related issues in a separate circuit? In the context of MOS vs CMOS, the power issue is the fact that CMOS uses less power MOS. Using NMOS-only circuity consumes more power, so how does a separate circuit resolve that?

    You can create a power-management circuit that puts the NMOS chip into sleep (basically disconnecting the VDD input). You probably want to implement that logic (counters, state machines, etc.) using CMOS logic, since that will be constantly on.

    Thanks for answering this very technical question! I've considered to buy the Lumix FZ1000, but then I've settled for a Canon (which uses CMOS). The camera arrives today... which makes me very happy. :)

    I didn't want to start an argument neither to be rude, sorry. What I meant is that I believe that (C)MOS is used as opposed to CCD, and there is no actual difference between MOS and CMOS in this context. Moreover, I can't find any evidence about it being nMOS or CMOS which are indeed different implementations of the MOS transistor technology. In the end, the sensor has to be either pMOS or nMOS. The bad thing is that the OP seems to have based the choice upon this difference.

    @clabacchio - there are various references to the "Live MOS" chips being an NMOS process which yields a different design to CMOS or CCD. The power/usage of an NMOS design would make more sense to Panasonic/Olympus as they produce a lot of EVIL and Compact cameras and few SLR's by comparison. For a definitive source on sensors it's worth a visit to the Chipworks website - the content's usually there, though finding what you need there can be a skill in itself!

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Content dated before 7/24/2021 11:53 AM