Chopper Stabilized, Low-Power, Low-Noise, Front End Interface Circuit for Capacitive CMOS MEMS Sensor Applications (original) (raw)
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International Journal of Electronics Letters, 2016
An accurate CMOS interface small capacitance variation sensing circuit for capacitive MEMS sensor applications An accurate front-end CMOS interface circuit for sensing very small capacitance changes in capacitive sensors is presented in this paper. The proposed structure scales capacitance variation to the sensible impedance changing. The scaling factor of the circuit can be easily tuned by adjusting bias points of the transistors. In order to cancel or decrease the parasitic components, the RC feedback and input transistor cascading techniques are used in the design. To simulate the circuit, HSPICE simulator is utilized to verify the validity of the theoretical formulations in 0.18 µm technology. According to schematic and post layout simulation results input impedance changes linearly versus capacitance variations up to 0.7 GHz while the sensor capacitance changing is varied between 0~200fF. Total dc power consumption is obtained as low as 1.2 mW with 1.8 V power supply.
On the Design and Optimization of a Switched-Capacitor Interface Circuit for MEMS Capacitive Sensors
In this paper a switched-capacitor (SC) interface circuit that is intended for MEMS capacitive sensors is proposed and designed. In the proposed architecture, both correlated double sampling (CDS) and chopper stabilization (CHS) noise reduction techniques are applied to the interface circuit to reduce the amplifier offset and low frequency noise. The effects of parasitic capacitances between the sensor and its interface circuit which are usually larger than the sense capacitances are carefully analyzed and used to optimize the readout performance. In other words, by analyzing the circuit offset and noise performance in presence of these parasitic capacitances, the suitable values of the circuit parameters such as sampling frequency, chopping frequency, and amplifier unity gain bandwidth are calculated. In comparison to the circuit using only CDS or CHS technique, the resolution variation of the proposed readout circuit is less than laF in presence of parasitic capacitances varying up to 20 pF.
Circuits Systems and Signal Processing, 2017
An accurate CMOS interface small capacitance variation sensing circuit for capacitive MEMS sensor applications An accurate front-end CMOS interface circuit for sensing very small capacitance changes in capacitive sensors is presented in this paper. The proposed structure scales capacitance variation to the sensible impedance changing. The scaling factor of the circuit can be easily tuned by adjusting bias points of the transistors. In order to cancel or decrease the parasitic components, the RC feedback and input transistor cascading techniques are used in the design. To simulate the circuit, HSPICE simulator is utilized to verify the validity of the theoretical formulations in 0.18 µm technology. According to schematic and post layout simulation results input impedance changes linearly versus capacitance variations up to 0.7 GHz while the sensor capacitance changing is varied between 0~200fF. Total dc power consumption is obtained as low as 1.2 mW with 1.8 V power supply.
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