Charge detector with long integration time

Abstract

The invention relates to an apparatus and method for detecting electrical charge with a long integration time and in particular to a sampling method which reduces noise that affects the accuracy of the measurement of the total charge. The apparatus samples the charge on the capacitor at the start of the integration period to obtain a sample proportional to a first noise component. It then samples the charge on the capacitor at the end of an integration period and subtracts the noise component sample from the integrated charge sample to obtain a measure of integrated charge to the relative exclusion of the noise component. The circuit uses a folded cascode amplifier and at least one correlated double sampling circuit. The charge detector can be used with any apparatus which generates electrical charge in response to an input including for example, a photodetector, photomultiplier, ion detector, e beam detector and piezoelectric charge detector and arrays of such devices.

Dependencies are inferred from the claim text.