Patent ID: 7525077

Claim:
A CMOS active pixel sensor, comprising: a photodiode for generating charge in response to incident light; a transmitting transistor for transmitting the charge stored in the photodiode to a sensing node; a dynamic voltage source for selectively providing a first power supply voltage and a second power supply voltage; a reset transistor, coupled to the dynamic voltage source, for resetting a voltage of the sensing node so that the sensing node has the fist power supply voltage; and a fingered type source follower transistor having a folded U-shaped gate electrode with a plurality of directly connected gate regions, a folded U-shaped source electrode with a plurality of directly connected source regions, and a drain electrode coupled to the dynamic voltage source, the fingered type source follower transistor receiving the voltage of the sensing node via the folded gate electrode to amplify the voltage of the sensing node and transmitting the amplified voltage into an internal circuit, wherein a channel width of the source-follower transistor is increased while a width of the fingered type source follower transistor is not increased in the longitudinal direction, so that the source-follower transistor is a symmetric structure.