How a CMOS Circuit Works

CMOS circuits are quickly replacing CCD image sensors in digital cameras because they are cheaper to manufacture and they consume much less battery power, which means photographers can take pictures longer. But, how does a CMOS circuit work?

CMOS as an Image Sensor

Just like a film camera, light passes through the lens and aperture onto the photographic medium. In the case of a digital camera, our photographic medium is a single chip CMOS image sensor. Before CMOS circuits, CCD (charge coupling device) image sensors were used in digital cameras. But, due to the fact that they are fairly expensive to produce and consume a lot more battery power, CMOS circuits have been gradually replacing them. As CMOS technology is becoming more advanced than CCDs, all digital cameras will eventually be produced with CMOS image sensors. 

CMOS stands for complementary metal oxide semi conductor. The CMOS contains the pixels that will eventually compose our digital image. Depending on the resolution of your camera, there could be thousands of pixels in the CMOS chip that will make up your photo.

Each pixel has a red, green and blue color filter. As the light photons his the CMOS senor, the color filters transform the photon data into an uncompressed digital form. That data is then transmitted to the computer processing system which interprets the RGB data into what is your image. Thus, CMOS circuits function as a bridge converting an analog medium (light) into a digital format (pixels).

CMOS Technology

The first patent for a CMOS circuit was issued in 1967 to Frank Wanlass. CMOS circuit's two important distinctions is that they're highly resistant to noise (thanks in part to the fact that they don't emit much heat), and they don't consume a lot of power. The most power consumption occurs in a CMOS circuit when it is be turned on and off. In fact, since 1976 CMOS circuits have been rated as having the best performance per watt in computer technology.

CMOS circuits operate by using field-effect transistors. Metal oxide semiconductor is a reference to the physical structure of these transistors. A metal gate electrode is placed on top of an oxide insulator. That is then on top of a semiconductor metal. A logic gate is formed and the circuit is able to operate.

CMOS circuits are mass manufactured just like other computer chips in Silicon Valley. They can work between the temperature ranges of negative 55 and 125 degrees Celsius.

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