New low noise interface circuit for detecting weak current of micro-sensors

TAN Xiao-yun¹, SUN-Ming¹, WANG Jia-qi¹, YIN Liang¹, LIU Xiao-wei^1,2

1.MEMS Centre,Harbin Institute of Technology,Harbin 150001,China;2.Key Laboratory of Micro-Systems and Micro-Structures Manufacturing,Ministry of Education,Harbin 150001,China



Abstract:

A new low noise interface circuit for detecting weak current of micro-sensors is designed.By using the transimpedance amplifier to substitute the charge amplifier,the closed-loop circuit can avoid the phase error of the charge amplifier.Therefore,the phase compensation devices will be cancelled,because there is no phase transformation through the transimpedance amplifier.As well as,by using CCCII devices to implement the high value feedback resistor of the impedance amplifier,the noise of the I-V transformation devices is reduced,comparing with the passive resistor.The floating resistor is easy to be integrated into chips,making the integration of the interface circuit of the intelligent sensors increase.Through the simulation,the phase error of the charge amplifier is almost 9°at 2 kHz and it changes with the working frequency of the micro-sensors making the phase compensation not easy.The value of the floating resistor is 250 kΩ where the bias current is 50 μA.The noise of the active resistor is 0.037 fV2/Hz,comparing with the noise of the passive resistor,which is 4.14 fV2/Hz.

Key words:  micro-sensor  weak signal detection  phase error  low noise

DOI：10.11916/j.issn.1005-9113.2011.04.003

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