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Integrating metal-oxide-decorated CNT networks with a CMOS readout in a gas sensor.

Lee H, Lee S, Kim DH, Perello D, Park YJ, Hong SH, Yun M, Kim S - Sensors (Basel) (2012)

Bottom Line: The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy.The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way.The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Seoul National University, Seoul, Korea. hyunjoong.lee@amic.snu.ac.kr

ABSTRACT
We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures.

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Dynamic range extension scheme to allow a greater range of charging times of an output capacitor to be measured. The improved timing ranges allow greater accuracy for simple and effective on-chip measurement of the current.
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f6-sensors-12-02582: Dynamic range extension scheme to allow a greater range of charging times of an output capacitor to be measured. The improved timing ranges allow greater accuracy for simple and effective on-chip measurement of the current.

Mentions: We use the dynamic range extension scheme shown in Figure 6 to increase the charging time that we can measure with a given range of detectable times. We introduce an on-chip switching reference resistor, a replica regulator and a replica time-signal generator, consisting of a comparator and a capacitor. The voltage drop across the cell and the on-chip reference resistor is the same, and each of the resulting currents charges an identical capacitor. The difference between the time required to charge these two capacitors is digitized by the read-out circuit. The resistance of on-chip reference resistor can be changed by a external digital code, which achieves a wide dynamic range.


Integrating metal-oxide-decorated CNT networks with a CMOS readout in a gas sensor.

Lee H, Lee S, Kim DH, Perello D, Park YJ, Hong SH, Yun M, Kim S - Sensors (Basel) (2012)

Dynamic range extension scheme to allow a greater range of charging times of an output capacitor to be measured. The improved timing ranges allow greater accuracy for simple and effective on-chip measurement of the current.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376610&req=5

f6-sensors-12-02582: Dynamic range extension scheme to allow a greater range of charging times of an output capacitor to be measured. The improved timing ranges allow greater accuracy for simple and effective on-chip measurement of the current.
Mentions: We use the dynamic range extension scheme shown in Figure 6 to increase the charging time that we can measure with a given range of detectable times. We introduce an on-chip switching reference resistor, a replica regulator and a replica time-signal generator, consisting of a comparator and a capacitor. The voltage drop across the cell and the on-chip reference resistor is the same, and each of the resulting currents charges an identical capacitor. The difference between the time required to charge these two capacitors is digitized by the read-out circuit. The resistance of on-chip reference resistor can be changed by a external digital code, which achieves a wide dynamic range.

Bottom Line: The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy.The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way.The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Seoul National University, Seoul, Korea. hyunjoong.lee@amic.snu.ac.kr

ABSTRACT
We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures.

Show MeSH