Circuit Design Of Mutifunction Cell Physiological Analysis Instrument

This thesis describes hardware and firmware design of the multifunction cell physiological analysis instrument based on the integrated chip for the recording of extracellular electrophysiological signals which is designed independent by our laboratory.This instrument is used to detect the response signals of the Microelectrode array, Light-addressable potentiometric sensor and Interdigitated sensor. Because of the feeble electrophysiological response signal of the cellular sensnor, the Lock-in technology is applied in the instrument for detecting the feeble current. Both analog Lock-in amplifier and ASIC+MCU for digital Lock-in amplifier are used.The analog Lock-in amplifier is applied to detect the response of the LAPS. DDS technology is used to buildup the dual orthogonal signal source. A low-current measurement system based on low input bias current operational amplifier is also included. The core of the Lock-in amplifier uses a high precision modulator/demodulator to complete multiplication demodulator and a lowpass filter which is used to filt out the DC signal.High precisionΣ-ΔADC is used for analog to digital conversion.The MCU communication with PC by UART or USB port.And the bias generator for LAPS sensor consists of high resolution DAC and high current buffer amplifier.The digital Lock-in amplifier is used for detecting the response of Interdigitated sensor.The system is based on the single chip impedance converter AD5933. Special attenuation circuit is designed for Interdigitated sensor. And the MSP430 MCU is used to complete the communication between the instrument and PC.The firmware is based onμC/OS-II real time operation system. The DDS,ADC,DAC and otherwise peripheral device driver and data collection, transmission,communication are completed under the multitask condition.The prototype has been fully checked and the result shows that all aspects of hardware reach the requirement.