Capacitive Sensor Interface Using an Inverter-Based Period Modulator

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Abstract

This thesis discusses the basic principles, circuit implementation and measurements of an inverter-based capacitive-sensor interface based on period modulation. The interface employs an inverter-based OTA and comparator to increase the current efficiency. Moreover, it applies new circuit techniques to reduce the die size and to reduce noise. A prototype interface has been implemented in a 0.16 ?m CMOS process to prove these concepts. The measurement results show that it can achieve more than 10 bit resolution consuming 14 ?A from a 1 V supply. The die size and energy efficiency have improved by more than an order-of-magnitude compared to previous interfaces based on period modulation.