When a switched capacitor circuit is constructed, a provision for output offset voltage generation by the effect of the clock feedthrough charge is indispensable. Especially in the circuit made of individual components using commercially available analog switches, this effect is significant.
In this paper, the generation mechanism of the feedthrough charge in an analog switch is analyzed and a circuit configuration method is proposed for compensation of the feedthrough effect for the integrator as the most fundamental switched capacitor circuit. Also, by a comparison experiment, with the conventional method, the effectiveness of the proposed circuit is confirmed.
The circuit size is larger as an integrator itself than the one by the conventional method. However, even in the case with a multiple cascading of the integrators such as in a higher-order filter, the feedthrough compensation is possible with only one feedback loop so that the overhead for the increased circuit size can be reduced. According to the trial circuit, the output offset voltage can be suppressed to the level of several millivolts. Hence, the present method can be applied to various operating circuits with high accuracy.