CMOS cameras operate at lower voltages than CCDs, reducing power consumption for portable applications. Analog and digital processing functions can be integrated readily onto the CMOS chip, reducing system package size and overall cost. Each CMOS active pixel sensor cell has its own buffer amplifier, and can be addressed and read individually. A commonly used cell has four transistors and a photosensing element. The cell has a transfer gate separating the photosensor from a capacitive "floating diffusion", a reset gate between the floating diffusion and power supply, a source-follower transistor to buffer the floating diffusion from readout-line capacitance, and a row-select gate to connect the cell to the readout line. All pixels on a column connect to a common sense amplifier.

