부산대학교 도서관

A simple integrated capacitance-to-frequency converter is presented. Its core is a switched-capacitor integrator. Under the control of a switch clock the converter produces a square-wave signal whose frequency depends on an external capacitor. It is insensitive to parasitic capacitance and not affected by the op amp offset voltage. Moreover, this converter has a linear capacitance-to-frequency transform characteristic. This experimental circuit has been implemented by a low voltage double-polysilicon 5-µm NMOS technology. Since the circuit is cost-effective and power consumption is low (less than 10 mW), such a converter is suitable for many mesurement systems which use a capacitor as a sensor. For example, it can be used for atmospheric pressure measurement in a meteorological balloon which cannot be reclaimed after release.