Research And Design Of Low Power And Low Noise Analog Front End For Low Frequency And Low Amplitude Signal

The development of portable medical devices has improved the ability to monitor patients and curbed the trend of morbidity in younger people.With the continuous breakthrough of CMOS technology,the integrated scale of circuits is constantly expanding,which creates conditions to produce portable monitoring equipment.As the primary component of portable equipment,the analog front end plays a decisive role in the circuit application scenario,circuit performance,and anti-interference ability.According to the electrode acquisition method and the integrity of the acquisition signal,human physiological signals can be classified.The amplitude is maximum in m V,and the frequency is lower than kilohertz.Due to the low amplitude and low-frequency characteristics,the signals are faced with lots of interference in the acquisition.In this paper,two low-power and low-noise analog front ends are researched and designed for low frequency and low amplitude signals under the constraint of a convenient scenario.The main contents are as follows:1.An AC-coupled ECG analog front-end for the heart-beat detection system is proposed.In the architecture,to cooperate with the heart-beat recognition,a differentiator is added for additional amplification,which realizes the recognition effect of the QRS waveform.To reduce the equivalent input noise of the circuit,transconductance bootstrap and source degradation structures are added to the instrument amplifier,achieving the value of 3.18μVrms.A new pseudo-resistor is used in the architecture to provide a DC path for the parasitic current,achieving up to 96 d B CMRR and GΩ level input impedance to meet the needs of the bioelectrical signal acquisition system.2.A dual-mode chopper Ex G analog front end is also proposed.In the architecture,to achieve the required amplification ratio of the EEG signal,the filter realizes multi-mode amplification,and the overall power consumption is only 1.2μW.Based on the chopper technology,the adaptive bias circuit is proposed in the instrument amplifier to relieve the voltage margin and widen bandwidth,and further reduce the equivalent input noise to 4.5μVrms,with the current reuse structure.An auxiliary module is added to enhance the input impedance of the circuit and the ability to suppress DC imbalance.a maximum common-mode rejection ratio of 118 d B,and an input impedance of 135 M,which increases the anti-interference of the whole system.