Analog Front-End for ECG Signal Acquisition with Automatic Gain Control

The electrocardiogram (ECG) requires accurate signal acquisition, achieved via an analog front-end (AFE) that amplifies and filters cardiac electrical signals. For compact, lowpower wearable devices, AFE design must balance gain, noise, and power consumption. This paper presents the design of an instrumentation amplifier for ECG signals using three two-stage Miller OTA amplifiers in 28 nm technology, achieving high gain and CMRR over 100 dB. It also includes a driven right leg amplifier, a low-pass filter (250 Hz cutoff) and a programmable gain amplifier (PGA) with gain ranging from $112.5 \mathrm{~V} / \mathrm{V}$ to $450 \mathrm{~V} / \mathrm{V}$. The proposed AFE successfully achieves a high common-mode rejection ratio (CMRR) of 104 dB and moderate power consumption of $14.427 \mu \mathrm{~W}$, meeting the key requirements for ECG signal acquisition in wearable biomedical devices. These results demonstrate the effectiveness of the design strategy, which combines Miller OTA-based instrumentation amplifiers, low-pass filtering, and programmable gain stages. This work highlights the feasibility of implementing low-power, high-gain analog front-end circuits in advanced CMOS technologies for compact, energy-efficient ECG monitoring systems.