Patent ID: 7304674

Claim:
A method of sampling image signals generated by multi-transistor pixel circuits of an active pixel sensor (APS) image sensor, the APS image sensor supporting a normal mode of operation and a sub-sampling mode of operation, the method comprising: providing a plurality of column amplifiers separate and distinct from the multi-transistor pixel circuits and coupled to output nodes of the multi-transistor pixel circuits, each column amplifier including an input configured to be coupled to a column of multi-transistor pixel circuits, an input capacitor coupled to the input of the column amplifier, an amplifier circuit, a first switch coupled between the input capacitor and the amplifier circuit, and a first node connected in series with the input capacitor and the first switch and positioned between the input capacitor and the first switch such that the input capacitor is positioned between the input and the first node; providing a plurality of second switches connected to the column amplifiers, each second switch being coupled between the first nodes of two of the column amplifiers; selecting a row of multi-transistor pixels circuits to sample; routing image signals from the output node of each multi-transistor pixel circuit in the selected row to a different one of the plurality of column amplifiers by opening the second switches when the APS image sensor is in the normal mode of operation; and routing image signals from the output nodes of a plurality of the multi-transistor pixel circuits in the selected row to a common one of the plurality of column amplifiers by closing at least some of the second switches when the APS image sensor is in the sub-sampling mode of operation, including exclusively routing multiple image signals from the output nodes of odd column multi-transistor pixel circuits to a common odd column amplifier of the column amplifiers and exclusively routing multiple image signals from the output nodes of even column multi-transistor pixel circuits to a common even column amplifier of the column amplifiers.