Analysis of 50 Hz Interference in the Biopotential Amplifier Circuit and Circuit Design
摘要
BACKGROUND: En some clinical applications or special work conditions, extremely intense 50 Hz AC interference exists. As the amplifier's output reaches or is close to saturation, it cannot be suppressed by general anti-interference circuits or software algorithms. Therefore, the hardware circuit must be improved to suppress thin interference, thus obtaining the desired signals. OBJECTIVE: To introduce a biopotential amplifier, which can effectively suppress the impact of 50 Hz AC interference on the weak biomedical signals. DESIGN: Create a circuit model based on the advanced theoretical analysis, then make software emulation and finally design the actual circuit implementation. SETTINGS: the 305 Hospital of Chinese PLA; Institute of Aviation Medicine, Air Force of Chinese PLA. MATERIALS: The experimental instruments and analytical software were provided by the Institute of Aviation Medicine, Air Force of Chinese PLA; the high-voltage electrical field environment was provided by the 305 Hospital of Chinese PLA. METHODS: The first step was theoretical analysis at the Institute of Aviation Medicine, Air Force of Chinese PLA in 2005, then the 50 Hz anti-reference model was created. After that, the following three anti-reference measures were put forward:① Enhancing the common-mode input impedance of the overall circuit to remove the interference caused by the imbalance electrode impedance; ② reducing the equivalent common mode input impedance of the instrument amplifier in the circuit by using a current source controlled by the common mode voltage; ③ using the driven-right-leg circuit to reduce the common mode voltage. Moreover, emulation analysis was made for the above Circuit model by using the circuit emulation software TINA PRO. Through ceaseless improvement of the circuit model, the correct emulation results were obtained. In 2006, the circuit model helped us realize the electrocardiogram (ECG) amplifier that could suppress the 50 Hz AC interference effective