Circuit Innovations for Wearable Biomedical Monitoring: CMOS Analog Front-Ends and Data Converter Architectures

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Wearable biomedical monitoring systems increasingly demand CMOS interfaces capable of operating under stringent energy, voltage, and environmental constraints while maintaining a reliable acquisition of weak physiological signals. In this context, analog front-ends (AFEs) and data converters have evolved toward increasingly co-designed architectures that jointly address power consumption, signal fidelity, electrode-interface constraints, and robustness to real-world perturbations. This review examines recent circuit innovations in CMOS AFEs and AFE–ADC interfaces for wearable biomedical monitoring with emphasis on the circuit-level mechanisms used to improve power efficiency, noise performance, dynamic-range management, interface robustness, and tolerance to variability and artifacts. The review first establishes the physical and circuit-level constraints governing low-power biomedical acquisition and then organizes standalone AFE techniques according to three complementary design objectives: power, precision, and robustness. Particular attention is given to architectures that integrate or redistribute conventional AFE functions within the data-conversion path, including functional absorption, analog-resource reuse, and signal-domain transformation. Representative implementations from approximately the last five years are compared using reported circuit and system metrics to identify the trade-offs associated with these architectural choices. The resulting perspective highlights the transition from isolated block optimization toward circuit and architectural co-design for energy-efficient, robust wearable biomedical interfaces.