Research And Design Of High-Performance Instrumentation Amplifiers In Bio-Signal Acquisition Front-End

With the development of social economy and the enhancement of personal health awareness,medical care has become the focus of human society.The collection and monitoring of bioelectrical signals such as electrocardiogram and electroencephalogram are of great significance for disease diagnosis.As the front end of the bioelectrical signal acquisition system,the instrumentation amplifier’s performance determines the reliability of the collected signal.The difficulty in the design of instrumentation amplifier is that it is still required to have low noise,high common-mode rejection,high linearity and high input impedance under the large common-mode fluctuation caused by power frequency interference,etc.Aiming at medical-grade bioelectrical signal acquisition equipment,this thesis designs a high-performance programmable gain instrumentation amplifier with rail-torail input/output voltage range.The instrumentation amplifier simplifies the conventional three opamp architecture,reducing the overall power consumption and area.The input stage of the main opamp adopts a folded cascode structure in which NMOS input pairs and PMOS input pairs are connected in parallel to achieve a rail-to-rail input voltage range.Pseudo-differential pairs compensation transconductance technology is used to remain transconductance constant within rail-to-rail input voltage range.The input stage combines chopping modulation technology to reduce low frequency noise and improve CMRR.The rail-to-rail output voltage range of the main opamp is achieved using a Class AB amplifier.Circuit and layout design,and circuit simulation are performed in 180 nm CMOS technology.The instrumentation amplifier has programmable gains of 1,2,3,4,6,8,and 12 V/V to suit different application needs.With a gain of 12 V/V and a supply voltage of 3 V,the quiescent current is 212 μA,the transconductance change rate is 5.04%in the rail-to-rail input common-mode range,and the CMRR at 50 Hz is 125.71 d B.The biosignal acquisition chip composed of modules such as the instrumentation amplifier and ADC has been successfully taped out with the 180 nm CMOS technology.The test results show that the input equivalent noise in the 4 k Hz bandwidth is 1.97 μVrms.When the output is 1.68 Vp,the dynamic performance of the signal path is as follows: THD is-113.97 d B,and the SNR is 105.54 d B.