# CMOS vs. VGA vs. VGA CCD



## Tacocaster (Jul 10, 2003)

I was wondering if anyone could enlighten me on the differences between CMOS vs. VGA vs. VGA CCD. Any help would be appreciated.


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## kiwiguy (Aug 17, 2003)

Your post is highly cryptic, and therefore difficult to guess just what info you want, and what it relates to.

CMOS=Complimentary Metal Oxide Semiconductor
VGA = Video Graphics Adapter (640 x 480 resolution implied)

VGA CCD = VGA as above and Charge Coupled Device

On a wild guess you are referring to video camera devices, then CMOS are cheap, but do not have the dynamic range of CCD. CMOS cameras "smear" with high contrast images.

CCD are better quality, and more expensive.

And VGA often (but not always) implies 640 x 480 resolution or that it connects to a VGA port on a PC.


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## vanderpol (Dec 13, 2002)

Uaually, people only compare CMOS image sensor with CCD image sensor; and nothing to do with the imager format such as VGA.
Image Quality: CCD imager is definitely better than CMOS since its temporal random noise and fixed pattern noise are lower than CMOS imager. The major reason is that charges generated in the CCD pixels are transferred all the way from pixels to amplifiers with more than 99.99999% efficiency. However, in CMOS imager, charges generated inside the pixels have to be converted to voltages and that suffers many kinds of noises such as KTC and row/column-based fixed pattern noise. In addition, the so-called CDS (correlated double sampling) method to reduce noises in CMOS imager is not as effective as in the CCD imager.

Power: CMOS imager is better since its technology can be scaled down together with the CMOS IC process; and therefore, the voltage can continue to decrease. Currently, CMOS imager can be manufactured with standard 1.8V/0.18um IC technology.

Cost: CMOS imager cost should be lower since its manufacturing process can be compatible with the mainstream IC technology with very minor modification. Companies start to integrate the CMOS sensor chip and image processing chip on the same chip; which is impossible for CCD imager due to its proprietary process.

Future Trend: CMOS image sensor quality may still be worse than CCD in the future due to its intrinsic pixel structures and due to its compatibility with the mainstream IC process which are only tailored for the digital ASIC or DRAM memory. However, for CMOS imager, due to its low-cost, low-power, and standard IC process, it will continue to erode the CCD market such as 1.3M/2.1M-pixels digital camera and cell-phone built-in camera.
For CCD, due to its long history of R&D and design/process experiences, will still continue to dominate for some time.


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