Research And Design Of High Performance Instrumentation Amplifier For ECG Acquisition Module

With the development and combination of biotechnology and microelectronics technology,the portable remote ECG monitoring and early warning system solves the "not timely" problem effectively has been proposed.In the portable remote ECG monitoring and early warning system,the effective detection of ECG signals characteristics is essential,because it will impact on the signal analysis results directly,so the system requires ECG signals acquisition module with high performance.And,the ECG signals are weak signals that are susceptible to noise interference,therefore high-performance instrumentation amplifier is an indispensable part of the acquisition module circuit.Instrumentation amplifier must have high gain performance and enable adjustable gain settings to amplify tiny signals to the appropriate voltage range in order to the benefit of analysis and processing for follow-up circuit.At the same time,the low frequency ECG signals will be affected by the common mode signals interference,therefore the instrumentation amplifier should have a high common mode rejection ratio to ensure the effectiveness of the signals.In view of the above problems,this paper presents a capacitive-coupled adjustable gain instrumentation amplifier,mainly composed of differential difference amplifier and variable gain amplifier.The main content of this paper is that according to the characteristics of ECG signals,setting the circuit performance indicators,and using the differential difference amplifier with chopper modulator as the preamplifier,which reduces the noise effectively and achieves the requirement of the high common mode rejection ratio.Next,using a variable gain amplifier with a feedback loop of a digital control gain as the second stage amplifier circuit to achieve the purposes of high and automatic-controlled gain.And achieving the circuit design,construction,simulation and layout through the Cadence software,finally formulating a chip test scheme to prepare for the chip test work.The main innovations of this paper are:(1)In the variable gain amplifier,using digital control circuit as the feedback loop,the way of digital-analog combination not only achieves automatic precision adjustment gain,but also minifies the chip area greatly;(2)In the first stage amplifier circuit,using pseudo resistance as the feedback resistor of differential difference amplifier closed-loop loop,it will have band-pass filter effect,suppressing the high-frequency ripple caused by chopping technology,the circuit is simple,and reduces noise interference effectively.Based on the SMIC 0.18?m CMOS technology,this paper completes the circuit design,construction,simulation,layout and tape-out.The circuit can achieves low power consumption,the common mode rejection ratio is 113.8dB,and adjustable gain,magnified 46 dB,54 dB and 60dB respectively.The supply voltage of the chip is 1.8V,the core area of chip is 678?m×598?m.