Cmos active pixel sensor with a sample and hold circuit having multiple injection capacitors and a fully differential charge mode linear synthesizer with skew control

An apparatus for processing a plurality of pixel signals, said apparatus comprising:

• a first circuit, comprising a first set of sample capacitors, a second set of sample capacitors, and a charge amplifier, said charge amplifier being controllably coupled to said first and second set of sample capacitors, for producing an analog correction signal;
• a second circuit comprising an amplifier, coupled to said first circuit, configured to receive an analog pixel signal from a first set of sample capacitors and, receive said analog correction signal from a second said of sample capacitors and produce a corrected analog signal by summing said analog pixel signal and said analog correction signal;
• and
• an analog-to digital converter configured to convert said corrected analog signal into a digital signal.

An imaging system comprising:

• a pixel array comprising a plurality of pixels;
• a controller, for supplying digital correction value corresponding to each of said plurality of pixels;
• a digital-to-analog converter, for converting an electrical signal output by one of said plurality of pixels into a digital signal;
• a storage device for storing said digital signal;
• and
• a circuit for correcting for an unwanted offset voltage in said pixel, said circuit for correcting further comprising:
• an offset correction circuit, coupled to said controller and receiving said digital correctional value and outputting an analog correction signal comprising at least first and second signal cells and first and second skew cells;
• and
• a sample-and-hold circuit, said sample-and-hold circuit further comprising a charge amplifier having a first input coupled to a first set of capacitors charged by an electrical signal produced by said pixel and a second input coupled to a second set of capacitors charged by the analog correction signal, and outputting a compensated signal as a linear function of the charge on said first and second sets of capacitors.