A VCII-based RC Sinusoidal VFO as Capacitive Sensor Interfaces

In this paper, a novel configuration of a sinusoidal variable frequency oscillator is presented. The circuit employs a single second-generation voltage conveyor as active element, so enjoys all the advantages of the current-mode approach. The circuit can be designed to have its oscillation condition independent of the value of one of its capacitances in a certain range. Due to this extremely attractive property, the circuit may be used as an electronic interface for capacitive sensors. A theoretical treatment of the circuit is provided to demonstrate its feasibility and to show the design process. Finally, both simulated and experimental result using off-the-shelf components are provided to validate the theoretical treatment and investigate the circuit performance as a capacitive sensor interface.