A system is described for correcting a switched input A/D converter circuit that performs a plurality of A/D conversions. The system includes an oversampling circuit, a switched input controller, separation circuitry, and a signal processing subsystem. The oversampling circuit is configured to convert one or more input analog signals into oversampled output signals. The switched input controller is configured to switch a separate calibration signal into the oversampling circuit, as a replacement for the input analog signal, for at least some of the A/D conversions. The separation circuitry is configured to separate the oversampled output signal from the calibration signal. The signal processing subsystem is configured to synchronously and separately process the oversampled output signal and the calibration signal so as to substantially reduce unwanted correlated response of the switched input A/D converter circuit.