巨磁阻生物传感器阵列及专用锁相放大器设计

Design of GMR Sensor Array and Its Locked Amplifier IC

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。

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 am- plifier IC of this system were described. This GMR chip includes 32 individually addressable GMR sen- sors and 2 reference sensors. Each sensor was a serpentine resistor trace 7/an wide with a total length of 1 mm with in a 100 vm-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 lag（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 YZ 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.