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A charge-coupled device stores photoelectrons in potential wells and transfers the charge through clocked stages to an output amplifier. The transfer differs from independently addressed pixels in a hybrid infrared detector.

In an imaging charge-coupled device, absorbed photons produce mobile charge carriers in a semiconductor; collection stores an electric charge packet associated with each optical detector pixel. Closely spaced MOS capacitors allow applied electric potential differences to move the packet from site to site. Willard Sterling Boyle and George Elwood Smith described storage, transfer and detection as distinct operations, including imaging as one application.^[ref]

The useful architectural trick is that many optical detector pixels can send their electric charge to a shared output electronic amplifier. This makes repeatable conversion possible but makes fidelity depend on every transfer along the route. An active-pixel sensor made with CMOS technology instead uses circuitry at pixels to convert or buffer their signal and select it for readout; independent pixel addressing does not require transporting each packet through the whole image. This compares readout architectures, not whether either technology can use a photodiode.^[ref]