Column-wise clamp voltage driver for suppression of noise in an imager

An imager comprising:

• an array of pixels organized into a plurality of rows and columns, each pixel having a transistor configuration and each column being connected to a column line;
• a row of clamp voltage drivers, each driver being associated with a respective column of the array and having a transistor configuration that is the same as the transistor configuration of the pixels in the associated column, each driver for generating a clamp voltage and for outputting the generated clamp voltage on a respective driver output line;
• and
• a plurality of sample and hold circuits, each sample and hold circuit being associated with and connected to a respective column line and driver output line, each sample and hold circuit for storing reset and pixel signals obtained from its respective column line based on the clamp voltage on its respective driver output line.

A CMOS imager comprising:

• an array of pixels comprising a plurality of imaging pixels organized into rows and columns, the array further comprising a row of column-wise voltage drivers, each driver being connected to and associated with a column of imaging pixels and outputting a clamp voltage;
• and
• a plurality of sample and hold circuits, each sample and hold circuit being associated with and connected to a respective column of imaging pixels and a respective voltage driver clamp voltage, each sample and hold circuit for storing signals obtained from its respective column using its associated clamp voltage;
• wherein each voltage driver comprises:
• a floating diffusion region for storing a reference voltage,
• a source follower transistor for converting the stored reference voltage into the clamp voltage, and
• a row select transistor for selectively outputting the clamp voltage to the respective sample and hold circuit.

An imager comprising:

• an array of imaging pixels organized into a plurality of rows and columns, each column having a column line;
• a row of voltage driver circuits, each voltage driver circuit being associated with a respective column and comprising means for generating a clamp voltage from a stored reference voltage;
• and
• a plurality of sample and hold circuits, each sample and hold circuit being associated with and connected to a respective column of imaging pixels and a respective voltage driver circuit, each sample and hold circuit comprising means for using the generated clamp voltage to store reset and pixel signals readout from a corresponding imaging pixel,
• wherein each voltage driver circuit has a transistor configuration that is the same as a transistor configuration of the imaging pixels in its associated column.