The reduction of low-frequency noise in feedback integrators

Two methods of designing a feedback integrator for use with repetitive inputs are described. Each results in a considerable improvement in signal/noise ratio compared with that of a conventional direct-coupled integrator. The first method uses an error amplifier containing a single CR coupling. In the second, phase correction is applied to the output from a low-accuracy direct-coupled integrator, increasing the accuracy but retaining the relatively high signal/noise ratio of the low-accuracy integrator.