Patent ID: 6025875
Filing Date: 2000-02-15
Classification: H04N

Abstract:
An apparatus including an analog signal sampler with improved correlated double sampling (CDS) performance for imaging systems, said analog signal sampler comprising:a first capacitive stage for selectively receiving an analog reference signal, a switched reference signal and an analog pixel signal and in accordance therewith charging to a first coupling charge state during a reference interval, providing a first plurality of transfer charges and charging to a second coupling charge state during an active interval, wherein said analog pixel signal includes a reference value during said reference interval and an image value during said active interval;a second capacitive stage for receiving said first plurality of transfer charges and said switched reference signal and in accordance therewith charging to a first sampling charge state during said reference interval, charging to a second sampling charge state during a first portion of said active interval, substantially maintaining said second sampling charge state during a second portion of said active interval and providing a first output signal which, in accordance with said second sampling charge state, corresponds to a first difference between said image and reference values of said analog pixel signal; anda switching stage, coupled to and between said first and second capacitive stages, for receiving said analog reference signal and a plurality of sampling control signals and in accordance therewith coupling said first and second capacitive stages during said reference interval and said first portion of said active interval, decoupling said first and second capacitive stages during said second portion of said active interval and providing said switched reference signal.