Browsing by Author "Chen, Yi-Chia"

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A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation
(2019-12-01)
Chen, Yi-Chia
;
Lu, Shao-Yung
;
Liao, Yu-Te
;
電機工程學系
;
Department of Electrical and Computer Engineering
An electrochemical sensing chip with an integrated current-reducer pattern generator and a current-mirror based low-noise chopper-stabilization potentiostat circuit is presented. The pattern generator, utilizing the current reducer technique and pseudo resistors, creates a sub-Hz ramp signal for the cyclic voltammetric (CV) measurement without large-size passive components. The proposed design adopts the chopper-stabilization and low-noise biasing technique for the potentiostat and a counter-based time-to-digital converter to reduce the amplitude noise effects and to convert the sensing current signal to digital codes for further data processing. The design is fabricated using a 0.18-m CMOS process and achieves a 41pA current resolution in the current range of 5A while maintaining the R-2 linearity of 0.998. The system consumes 16W from a 1.2V supply when a 5A sensing current is detected. The power efficiency of the readout interface is 0.31, and the sensing current dynamic range is 108dB. The design is fully integrated into a single chip and is successfully tested in the dual-mode (CA/CV) measurements with commercial gold electrodes in a potassium ferricyanide solution in sub-millimolar concentrations.
A Power-efficient Bidirectional Potentiostat-based Readout IC for Wide-range Electrochemical Sensing
(2018-01-01)
Tsai, Jui-Hsiang
;
Chen, Yi-Chia
;
Liao, Yu-Te
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper presents a low-power electrochemical sensor readout IC with a bi-directional potentiostat for accommodating a large dynamic sensing current range. The proposed chopper stabilization potentiostat, suppressing low-frequency noise at the front end and providing stable positive and negative potentials between the working and reference electrodes for bi-directional current sensing through a switched push-pull readout stage. The digital implementation of an oscillator-based current to frequency converter and frequency counter transforms the sensing current directly into digital codes. The design is realized in a 0.18 mu m CMOS process and occupies an area of 1.3mm(2), including all passive components and pads. The proposed readout IC achieves a 0.9pA minimum detectable current in a current range of +/- 18 mu A, an R-2 linearity of 0.999, and a dynamic detectable current range of 152dB. The static power consumption of the proposed readout IC is 2.9 mu W from a 1.5V supply.
A Power-efficient, Bi-directional Readout Interface Circuit for Cyclic-voltammetry Electrochemical Sensors
(2019-01-01)
Chen, Yi-Chia
;
Lu, Shao-Yung
;
Tsai, Jui-Hsiang
;
Liao, Yu-Te
;
電機工程學系
This paper presents an electrochemical sensing front-end circuit with a cyclic voltammetry potentiostat. To accommodate a large and bidirectional current sensing range for the current-mirror based potentiostat, a constant offset current is added. With the technique of chopper-stabilization, the flicker noise of the readout circuit is successfully reduced. A charge-based oscillator is also proposed in this paper to convert the current into a frequency for further data readout. The proposed readout IC was fabricated in a 0.18 mu m, 1.2V CMOS process and the current range is -2 mu A similar to 12.2 mu A, the R-2 linearity of 0.992, with a minimum detectable current of 3.1nA. The dynamic current range is 73.2dB whereas the chip consumes 40.5 mu W at a maximum sensing current of 12.2 mu A.