Noise analysis of a capacitor-to-voltage converter with a zoom-in technique

We report the noise analysis of a capacitor to voltage converter (CVC) with a zoom-in concept, used as a first stage in capacitive sensor interfaces for measuring very small capacitance variations. We will show that the zoom-in concept introduced in the first stage can not only relax the resolution requirement of the following stages, i.e. an analog-to-digital converter (ADC), but it can also increase the resolution of the capacitor to voltage converter itself. It will be also proven that, for a given measurement time, the resolution of the input stage of the CVC is independent of the load capacitor. This is true both with and without zoom-in technique. This finding can make the design of the complete system more flexible. We will show that such a system is very efficient for high resolution displacement measurement, based on a capacitive sensor system.