Here's something more technical for a change! The Nikon D90 CMOS sensors employs a technology in which both the photodiode and a readout amplifier are incorporated into a pixel. The technology is known as ‘active pixel sensor’ (APS).
Unlike the CCD, the charge accumulated at each photosite in a CMOS sensor is converted into an analogue voltage in each pixel and the voltage from each pixel is connected to a common readout line using switching transistors in each pixel. The photodiode and associated amplification circuitry are arranged on an x–y grid.
A comparison table is provided above to compare CCD and CMOS sensor technologies.