Key result
The proposed 180 nm CMOS ECG/ETI sensor system achieved a high output impedance of 1 MΩ at 500 kHz, detected resistance from 10 mΩ to 3 kΩ, and consumed 3.6 mW using a 1.8 V supply.
The proposed integrated ECG/ETI sensor system demonstrates high output impedance, wide detection ranges, and low power consumption suitable for advanced physiological monitoring.
An active electrode (AE) and back-end (BE) integrated system for enhanced electrocardiogram (ECG)/electrode-tissue impedance (ETI) measurement is proposed. The AE consists of a balanced current driver and a preamplifier. To increase the output impedance, the current driver uses a matched current source and sink, which operates under negative feedback. To increase the linear input range, a new source degeneration method is proposed. The preamplifier is realized using a capacitively-coupled instrumentation amplifier (CCIA) with a ripple-reduction loop (RRL). Compared to the traditional Miller compensation, active frequency feedback compensation (AFFC) achieves bandwidth extension using the reduced size of the compensation capacitor. The BE performs three types of signal sensing: ECG, band power (BP), and impedance (IMP) data. The BP channel is used to detect the Q-, R-, and S-wave (QRS) complex in the ECG signal. The IMP channel measures the resistance and reactance of the electrode-tissue. The integrated circuits for the ECG/ETI system are realized in the 180 nm CMOS process and occupy a 1.26 mm2 area. The measured results show that the current driver supplies a relatively high current (>600 μApp) and achieves a high output impedance (1 MΩ at 500 kHz). The ETI system can detect resistance and capacitance in the ranges of 10 mΩ–3 kΩ and 100 nF–100 μF, respectively. The ECG/ETI system consumes 3.6 mW using a single 1.8 V supply.
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Nguyen et al. (2023) studied this question. Active-electrode ECG/ETI sensor system was evaluated on System performance (current driver output, impedance detection range, power consumption). The proposed 180 nm CMOS ECG/ETI sensor system achieved a high output impedance of 1 MΩ at 500 kHz, detected resistance from 10 mΩ to 3 kΩ, and consumed 3.6 mW using a 1.8 V supply.
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