The Gmr Biosensors Dedicated Lock-in Amplifier Chip Design

Been a new kind of device, GMR biosensor got quick development in recently years. It is widely used in particular fields as bio-chemicals and bio-physicals. Generally, GMR biosensor is composed with GMR sensor, chip of lock-in amplifier and immune magnetic remarks. As we kown, GMR sensor technology is not mature, and still in researching. At the same time, commercial lock-in amplifier has some problems, for example, large cubage and expensive.In order to solve the problems, we design a GMR sensor chip for GMR biosensor. In consider with output signal, a lock-in amplifier chip is employed for GMR biosensor. GMR sensor has high MR, high sensitive performance and so on. Lock-in amplifier chip integrate with LNA and BPF, greatly enhance the practicability of GMR biochips.The GMR sensor chip has 16 sensor cells and one standard cell in the structure. We utilize technology advantage and manufacture flat of State Key Laboratory of Magnetism, Institute of Physics, CAS; In order to produce GMR sensor with high MR,high sensitive and low coercive force performance. After this, we have done GMR sensor's magnetic field test. The results show GMR sensor can match with LIA well in the noise. The basic block scheme of the lock-in amplifier which proposed in this dissertation employed the structure of orthogonal vector′s LIA, We have made the following revision: 1) integrate with LNA and BPF in LIA, by way of LIA's first class; 2) added odd to double transformation circuit, frequency multiplier and square-wave transformation circuit in the reference channel. The block scheme of the lock-in amplifier mainly consisted of four modules. It is low noise amplifier, signal modulate, signal transformation circuit and bandgap benchmark source. The circuit was simulated via Cadence spectre based on Chartered 0.35um process, whose results indicates that all modules have meet the requirements and the system could detect the weak signal even its amplitude lower than 1μV. After this, we produce the LIA by chartered company in Singapore, and encapsulate in Gansu province. Finally, we design and produce the test PCB, and the test results show that the specifications have met the design requirements.