Sensor Readout Interfaces
Nanomaterials such as Carbon Nanotubes (CNTs) are explored as sensing elements in various Internet-of-Things (IoT) applications, e.g. in air quality monitoring systems.
To interface an NO2 gas-sensor, dedicated, portable and power efficient systems, which can bias, reset, acquire sensor output signals and store them on an SD card or send them via BLE are being developed.
One such system, is composed of an adjustable CNT voltage bias with an 28 mV step, which controls a regulated cascode for current-mode readout. It is followed by a TIA with 109 dBOhm gain and 1 dBOhm gain flatness, 2 pA/sqrt(Hz) noise, 4 µA input range with noise filtering included, and differential output. The latter is connected to a 9-bit SAR ADC of 86 fJ/conv. The design is realized in 180 nm CMOS technology and occupies a silicon area of 0.18 mm2.
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