巨磁阻生物传感器阵列及专用锁相放大器设计

EW_GⅠ是基于GMR(巨磁阻)传感器,用于检测血样中特种病毒的正在研发的生物芯片系统。叙述了其巨磁阻传感器阵列以及后端锁相放大IC电路的设计及实现。该阵列包含32个GMR传感器单元和2个传感器参考单元,形成多路的半桥式惠斯通电桥,用于感应绑定磁球的附加磁场。每个单元(100μm×100μm)由长1mm、宽7μm的巨磁电阻蜿蜒而成,该电阻采用Ag(2nm)/NiFe(6nm)/Cu(2.2nm)/CoFe(4nm)]20结构,采用Ag作为镜面层,其饱和磁场小于等于30mT,GMR值约6%,单个传感器电阻约为780Ω。配套的锁相放大芯片包括了信号通道、参考通道、前置低噪声放大器、带通滤波器、可控增益放大器、相敏检测电路、正交移相电路、差分直流放大电路八个部分,整个设计功耗小于50mW@Vcc=3V。

Design of GMR Sensor Array and Its Locked Amplifier IC

EW_GⅠ based on the giant magnetoresistive(GMR) sensors is a developing biochip system used to detect the virus in blood sample.The design and performance of current chip and the locked amplifier IC of this system were described.This GMR chip includes 32 individually addressable GMR sensors and 2 reference sensors.Each sensor was a serpentine resistor trace 7 μm wide with a total length of 1 mm with in a 100 μm-diameter circular zone.One sensor and one reference sensor on the chip were used as a half of one Wheatstone bridge.Each sensor trace was composed of an uncoupled magnetic/ nonmagnetic/ magnetic GMR sandwich with structure Ag(2 nm)/NiFe(6 nm)/Cu(2.2 nm)/CoFe(4 nm)]20.The first nonmagnetic layer,a 2 nm thick Ag,was used to be specular layer.The bulk material had a sheet resistance of 780 Ω and a GMR response of 6% at the saturation field of 30 mT.The lock-in amplifier was divided into eight main sections: a signal channel,reference channel,frequency multiplier,pre-low-noise amplifier,variable gain amplifier,phase detector circuit,quadrature phase shift, DC differential amplifier.The power design of the total IC is below 50 mW@Vcc=3 V.