How to suppress noise is necessary to consider the question of focus in hardware design.The external noise can be avoided or reduced by the way of reasonable design.The variety of influencing factors on power supply noise of the operational amplifier circuits are analyzed in more details and put forward corresponding solutions,in order to more fully exert low-noise op amp performance.

Since the body is a good conductor,the pacing signals and cardio-signals can be acquired together by ECG measuring circuit. The high pacing signals interfere with the processing of cardio-signal. This paper introduces a new method for restraining pacing signals and compares it with the traditional one based on slew inhibition. The result indicates that the new method is superior to the traditional one.