Sense amplifier for high-density imaging array

A sense amplifier for use in a photosensing array including a plurality of photosensing elements arranged in an array of rows and columns, each column having a column width, the sense amplifier comprising:

• an input node;
• an output node;
• an input transistor having a gate connected to the input node, a source connected to a first supply voltage rail, and a drain;
• a cascode transistor having a gate connected to a cascode node, a source connected to the drain of the input transistor, and a drain connected to the output node;
• a load transistor having a gate connected to a bias node, a drain connected to the output node, and a source connected to a second supply voltage rail;
• wherein the w/l ratio of the input transistor and the cascode transistor is much greater than the w/l ratio of the load transistor;
• and
• wherein said sense amplifier may be disposed in an area on an integrated circuit, said area having a width no greater than the column width.

A sense amplifier comprising:

• an input node;
• an output node;
• an input transistor of a first conductivity type having a gate connected to the input node, a source connected to a first supply voltage rail, and a drain;
• a cascode transistor of said first conductivity type having a gate connected to a cascode node, a source connected to the drain of the input transistor, and a drain connected to the output node;
• and
• a load transistor of a second conductivity type opposite that of said first conductivity type having a gate connected to a bias node, a drain connected to the output node, and a source connected to a second supply voltage rail;
• wherein the w/l ratio of the input transistor and the cascode transistor is much greater than the w/l ratio of the load transistor.

A sense amplifier for use in a photosensing array including a plurality of single-transistor photosensing elements arranged in an array of rows and columns, each column having a column width, the sense amplifier comprising:

• an input node;
• an output node;
• an input transistor of a first conductivity type having a gate connected to the input node, a source connected to a first supply voltage rail, and a drain;
• a cascode transistor of said first conductivity type having a gate connected to a cascode node, a source connected to the drain of the input transistor, and a drain connected to the output node;
• a load transistor of a second conductivity type opposite that of said first conductivity type having a gate connected to a bias node, a drain connected to the output node, and a source connected to a second supply voltage rail;
• wherein the w/l ratio of the input transistor and the cascode transistor is much greater than the w/l ratio of the load transistor;
• and
• wherein said sense amplifier may be disposed in an area on an integrated circuit, said area having a width no greater than the column width.