Current conveyor-based differential capacitance analog interface for displacement sensing application

A current conveyor-based analog electronic interface for differential capacitive sensors is here shown. The read-out circuit that utilizes second generation Current Conveyors (CCIIs) as active blocks is able to evaluate differential capacitive variations performing a capacitance-to-voltage conversion. This solution has been implemented both in a discrete element board and as integrated version in a standard 350 nm CMOS technology. Simulations and experimental results have shown a linear input/output characteristic and a good agreement with theoretical expectations, being the former performed for both the designed solutions, whereas the latter only for a discrete prototype board (employing a low cost commercial component (AD844). Sensitivity and resolution data on a practical case-study of a displacement sensor are constant and their values are satisfactory. Both simulated and measured results make the proposed architecture a good candidate as first stage of analog front-ends to be employed in differential capacitive instrumentation.