Acetone vapor sensing is important for environmental monitoring and non-invasive screening of diabetes mellitus (DM). Inhaling higher than 176 parts per million (ppm) acetone concentrations affects the respiratory system, while acetone in exhaled breath correlates with blood glucose and exhaling more than 1.8 ppm indicates the person is in danger of DM. DM is currently diagnosed invasively by measuring glucose level in blood, which is painful, and therefore inconvenient. This paper reports MEMS sensor device functionalized with blend of Chitosan/Polyethylene glycol polymers for acetone vapor sensing for possible non-invasive screening of diabetes. The sensor was experimentally tested using synthetic acetone vapor, and found to give linear response for 0.05-5 ppm acetone in air, with a sensitivity of 21 mV/ppm, good repeatability, response, and reversibility. Cross-sensitivity for 2-propanol and methanol was examined, where the responses of the sensor to 1 ppm concentration in air of these two analytes were found to be 24% and 33%, respectively, less compared to its response to the same concentration of acetone.

In this paper, a chopper stabilized fully differential CMOS pre-amplifier circuit is presented. The proposed circuit is designed for sub-atto Farad capacitive CMOS MEMS sensing applications. Chopper stabilization technique is employed to minimize flicker (1/f) noise and offsets in the circuit. The proposed circuit is designed using MIMOS 0.35 ?m AMS CMOS 3.3 V technology and simulation results from Cadence Virtuoso Spectre circuit simulator show that the proposed circuit is able to detect capacitance changes ranging from 0.0375 aF to 37.5 fF, attain an input inferred noise of 0.9 nV/ , gain of 18.1 dB at 3-dB frequency of 5.5 MHz with total power consumption of 0.33 mW.

In this work, we propose a PMOS based wide swing cascode current mirror (WSSCM) for 0.35 um CMOS-MEMS technology. The proposed circuit shows a high bandwidth current mirror with high output resistance capability operating at low voltage levels. Noise, output resistance and bandwidth analysis are presented. CADENCE SPECTRE circuit design tool using MIMOS 0.35 um and BSIM3 transistor models is used to carry out the simulations. The circuit achieves an amplification of 120.04 uA, the input referred noise of the circuit is 75.77 nV/√Hz with a minimum power consumption of 0.33 mW and a high output resistance of 15 MO .

This paper presents a design and technique for low noise, low offset modulation demodulation circuit for chopper stabilized amplifiers use in CMOS-MEMS sensor applications. In these sensors, where the sensed signals are usually very weak, a low-noise interface readout circuit plays a crucial role in determining the overall sensor performance and success in the market. Amplifiers are the core building blocks of these circuits and hence there is a growing demand for low noise and low offset designs and fabrication. Chopper stabilization technique has been widely used in amplifiers for flicker (1/f) noise and offsets reduction purposes using the principles of modulation and demodulation. Thus, the functionality and performance of the modulation and demodulation circuit determines the realization and attainment of chopper stabilization. The demonstrated circuits in this work are designed in MIMOS 0.35 μm AMS CMOS 3.3 V CMOS process technology. Cadence Spectre simulation results show the presented circuit achieves chopper stabilization with total noise contribution of 0.885 nV√Hz and minimized offset.

This paper presents a monolithic, low-noise capacitive readout interface circuit for CMOS-MEMS resonator based gravimetric chemical gas sensors. In these sensor devices, where the sense capacitances are usually very weak, the readout interface circuit plays a crucial role in determining the overall sensor performance. Noise is observed in various active and passive devices affecting circuit performances. Particularly at low frequencies, flicker noise is dominant in degrading the quality of output signals. A dual stage, open-loop continuous time voltage sensing with chopper stabilization technique is proposed in this work to cope with it and improve the total output signal SNR. The proposed circuit is designed based on MIMOS 0.35 μm AMS 3.3V CMOS technology. Cadence Spectre circuit simulator simulation results show, the proposed circuit achieves an input inferred noise of 11.6 n V/√(Hz), total gain of 48.1 dB and consumes a total power of 3.385 mW. The designed circuit is able to detect minute capacitance changes as low as 0.0365 aF with total sensitivity of 67.95 μV/aF.