Design and Optimization of a Low-Power ECG Signal Amplifier using Self-Cascode OTA in 90nm CMOS Technology

This work uses a low-power operational transconductance amplifier (OTA) to operate at low input voltage levels, representing the electrocardiogram (ECG) signal input in a 90nm technology node. The design methodology involves sizing of the transistors for the desired gain by g _m /i _d methodology and by implementing self-cascode transistors for a larger effective channel length. The design employs a two-stage design, a differential input for the first stage, and a common source amplifier with PMOS input for the second stage. The Cadence Virtuoso design tool simulates the design using the GPDK90 library. The proposed design is given an AC amplitude of 10mVp-p at 250Hz to represent ECG input signal level application of VDD and VSS of + 0.5V and − 0.5V, respectively. The designed OTA offers a gain of 81.1928 dB with a bandwidth of 176.928Hz and a unity gain bandwidth of 1.32MHz. The design's power consumption is observed to be 280.2321nW with CMRR and PSRR of 83.24dB and 83.12dB, respectively, and the integrated IRN is found to be 10. 32µV _rms . The post layout design results in an area of 4390 µm ² . The design is also simulated with an ECG signal from the MIT BIH dataset, the gain is found to be 81.0112dB at 180.083Hz with unity gain bandwidth of 1.29MHz, with other parameters remaining the same compared to the sinusoidal equivalent signal.