Design and implementation of interface circuits for nanowire field-effect-transistor sensors

• Main Authors: Chen, Liang-Hsun, 陳亮勳
• Other Authors: Chen, Tsung-Lin
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/46824778364341779495

碩士 === 國立交通大學 === 機械工程系所 === 104 === Silicon Nanowire field-effect-transistors (SNWFET) are biosensors which produce different currents when immersed to different concentration of solution samples. Since the current output of SNWFETs normally varies from femto amperes to micro amperes, they are connected to high-end apparatus, which can detect tiny current variation in a large range, in practical sensor applications. Unfortunately, these high-end apparatus are often expensive and difficult to carry, which may limit the promotion of SNWFET sensors. The aim of this research is to design suitable interface circuits to replace the high-end apparatus in SNWFET sensor applications. In this research, we proposed two circuit designs based on the characteristics of SNWFETs designed/ fabricated by professor Yang’s research group [1]. The first design is referred to as “single-end amplifier” in this report, which consists of two-stage transimpedance amplifier, auto-zeroing amplifier, feedback capacitor, low pass filters, multiplexer, digital potentiometer, and etc. It can measure 16 SNWFETs simultaneously and convert pico ampere currents into voltage for subsequent signal processing. Because the performance of SNWFETs can be greatly affected by the fabrication process and testing environment, the relative value of the sensor measurement taken before and after the chemical reactions is more important than the absolute value of the sensor measurement taken after the chemical reactions. Thus, this research proposed the second design which is referred to as the "differential-mode” interface circuits in this report. The differential-mode sensing circuit employs an additional reference SNWFET device to form a differential mode measurement. Besides, both the feedback control and switching capacitor techniques are employed to compensate the mismatch between two SNWFET and the noise/drift of the circuit components.