Study Of A Readout Circuit For Neural Biosensor Micro Arrays

The neurobiology sensing microarray for the biological sensors is used to detect brain nerve signals. It is combined with microelectronics technology and neural biology. This paper targeted on the 1×4 neural sensor micro array weak voltage signal, studied the CMOS readout circuit and the fabrication of neural micro probe. It can do some prepare for integratting CMOS readout circuit and neural micro probe.This paper targeted on the neural bio-sensor micro array, introduced the basic structure of neural micro probe, and analyzed the characteristic of voltage output signal, based on the response of electrode probe, built the electrical model of micro electrode.Preamplifier circuit is an important part of readout circuit. This paper designed a preamplifier based on the feed-forward compensation technology. Because of tooking the feed-forward compensation technology, the amplifier not only avoided the influence of integrating Miller compensation capacitor on the chip, but also solved the interaction problem during gain, bandwidth and phase margin in traditional circuit design. It is satisfied the need of low voltage, low power consumption of micro electrode signal. After analyzed the advantage and disadvantage of resistance feedback network and capacitor feedback network, this paper took the capacitor feedback network as the closed loop feedback structure.Because the feed-forward amplifier is not sufficient to process the signal, this paper also designed a second stage amplify circuit. The second stage circuit took the rail to rail structure operational amplifier. After analyzing the basic structure of circuit, it got the result of simulation. The second stage took the capacitor feedback network as closed loop feedback structure.This paper analyzed various noise of readout circuit, took an Correlate Double Sample structure, analyzed the theory of double sample, and simulated the structure.For the micro sensor array, it is necessary to design data selective gate to control the unit of micro probe sensor array. The data selective gate was made of shift register, inverter and transmission gate. The shift register as the key part of data selective gate, took quasi-static CMOS shift register, which had the advantage of using less devices and low power consumption. At last, this paper exhibited the simulation results of quasi-static CMOS shift register and data selective gate.It is designed a band gap circuit with simple structure, analyzed the theory of band gap circuit, and gave the simulation result.After the simulation of the circuit, this paper introduced the problems needed to pay attention to during layout. It took 0.5μm standard CMOS procedure specification, and gave the layout of each unit, designed the layout, and had the DRC, LVS test to layout.At last, the paper discussed the fabricate process chart of neural micro probe by tooking surface sacrifice layer technology.