A 0.5-V 17.5-nW MI-OTA-based universal filter with independently and electronically tunable $${{\varvec{\omega}}}_{{\varvec{o}}}$$ and $${\varvec{Q}}$$ in 65-nm CMOS

Ultra-low-power analog signal processing circuits are essential for energy-constrained biomedical systems. This paper presents a novel gate-driven multiple-input operational transconductance amplifier (MI-OTA) designed in 65-nm TSMC CMOS technology, operating at a 0.5 V supply voltage. The proposed MI-OTA achieves an extremely low bias current of 2 nA and consumes only 3.5 nW. By exploiting multi-input capability, the architecture enables compact analog signal processing with reduced active element counts. As a proof of concept, a universal filter with an independently tunable quality factor is realized. The filter achieves a 58 dB dynamic range and 1% THD at 100 mV input, while successfully suppressing high-frequency ECG interference. The design robustness is verified through comprehensive simulations, demonstrating its suitability for long-term sensing applications. The proposed filter topology is further validated experimentally using commercially available LM13700N ICs.