Current-Mode Capacitive Sensor Interface Circuit With Single-Ended to Differential Output Capability

This paper presents a current-mode interface circuit for capacitive sensors, with the main features being its ability to produce a differential output from a single-ended sensor (using a fixed reference capacitor) and its simplicity in realization. These advantages make it a potential candidate for...

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Bibliographic Details
Published in:IEEE transactions on instrumentation and measurement 2009-11, Vol.58 (11), p.3914-3920
Main Authors: Singh, T., Saether, T., Ytterdal, T.
Format: Article
Language:English
Subjects:
Capacitance measurement
Capacitive sensors
Capacitors
Circuit testing
CMOS process
Differential amplifiers
interface for capacitive sensors
microsensor interface
Operational amplifiers
Prototypes
Sensor phenomena and characterization
Sensors
Silicon
single ended to differential
Transconductance
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Summary:This paper presents a current-mode interface circuit for capacitive sensors, with the main features being its ability to produce a differential output from a single-ended sensor (using a fixed reference capacitor) and its simplicity in realization. These advantages make it a potential candidate for applications where differential sensors are not available and where a simple design is required. The principle is, however, easily applicable to differential sensors as well. The interface concept can be realized in different ways; however, to present a proof of concept on silicon, a prototype has been fabricated and tested in a commercially available 0.8-mum CMOS process. The circuit has been designed using common analog building blocks such as a fully differential operational transconductance amplifier (OTA), a high-output-resistance wide-swing current source, and a single clock phase. The estimated linearity error was 0.2% relative to full-scale swing with a simple two-point calibration. The circuit consumes 145 muA from a 5-V power supply.
ISSN:0018-9456
1557-9662
DOI:10.1109/TIM.2009.2021241