A ECG offset cancelling readout circuit using a current mode feedback loop technique

Abstract

This paper presents an instrumentation amplifier for ECG signals, compared with the traditional three op amp ECG read instrumentation amplifier, the circuit overcomes the disadvantage of low common mode rejection ratio due to resistance mismatch of the three operational amplifier. At the same time, the circuit uses the inverting integral amplifier as an DC offset feedback circuit to eliminate the offset voltage at the input of the amplifier. This circuit implements the class-AB control circuit to achieve high linearity output. The circuit is compact with few peripheral components. The circuit is designed and implemented by using 0.18 um CMOS Technology. The circuit test results show that the circuit can eliminate the input offset voltage of the 140 mv. And has a DC gain of 40 dB and a common mode rejection ratio (CMRR) of 120 dB at the 2 V supply voltage. THD is −64 dB, and the total input reference noise is 0.78 µVrms, the power consumption is 121.6 µW, the bandwidth is 2 kHz.