Patent ID: 6018364
Filing Date: 2000-01-25
Classification: H04N

Abstract:
A correlated double-sampling circuit that removes any noise or offsets common to an input signal of the correlated double-sampling circuit, the circuit comprising:a first sampling cell including a first sample-and-hold circuit responsive to a first clock signal, the first sample-and-hold circuit disposed in parallel between the input of the correlated double-sampling circuit and an output of the correlated double sampling circuit, with a second sample-and-hold circuit responsive to a second clock signal, each of the first sample-and-hold circuit and the second sample-and-hold circuit having an input coupled to the input of the correlated double sampling circuit, the first sample-and-hold circuit having a first output providing a first output signal that is a first sample of the input signal and the second sample-and-hold circuit having a second output providing a second output signal that is a second sample of the input signal;a second sampling cell disposed in parallel with the first sampling cell between the input of the correlated double sampling circuit and the output of the correlated double sampling circuit, the second sampling cell including a third sample-and-hold circuit responsive to a third clock signal and a fourth sample-and-hold circuit responsive to a fourth clock signal, the third sample-and-hold circuit and the fourth sample-and-hold having respective inputs coupled to the input of the correlated double-sampling circuit, the third sample-and-hold having a third output providing a third output signal that is a third sample of the input signal and the fourth sample-and-hold circuit having a fourth output providing a fourth output signal that is a fourth sample of the input signal; andselecting means for taking a difference between two signals of the first output signal, the second output signal, the third output signal and the fourth output signal to provide a first difference signal and for taking a difference between an alternate two signals of the first output signal, the second output signal, the third output signal and the fourth output signal to provide a second difference signal, the selecting means selecting one of the first difference-signal and the second difference signal and providing a filtered signal at the output of the correlated double sampling circuit.