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This paper presents two alternative zoom-in techniques, suitable for two widely used classes of capacitive sensor readout circuits. The zoom-in approach is useful, when the variation of the capacitance to be measured is much smaller that its nominal value. By applying a zoom-in technique in the front end stage of the sensor readout circuit, the dynamic range requirement for the following stages, including the analog-to- digital converter, is significantly reduced. The analysis shows that for high-speed high-resolution capacitive sensor interfacing tasks, readout circuits based on capacitive to voltage converter is more practical. [ABSTRACT FROM AUTHOR]