A 0.5 V 1.35 nW Fourth-Order DTMOS-Based Flipped Voltage Follower Low-Pass Filter with 70 dB Dynamic Range for ECG Signal Acquisition

This paper presents a fully differential fourth-order low-pass filter (LPF) designed for ultra-low-power ECG acquisition systems. The design utilizes a dynamic threshold MOSFET (DTMOS)-based flipped voltage follower (FVF) topology to meet the stringent requirements of wearable and implantable biomedical electronics. By leveraging DTMOS input transistors and operating the circuit in the subthreshold region, the filter achieves extreme power efficiency, consuming only 1.35 nW from a 0.5 V supply. The proposed architecture was simulated using 150 nm CMOS technology in Cadence Virtuoso. Simulation results demonstrate a cutoff frequency of 132.68 Hz with 0 dB passband gain, making it ideal for capturing the clinical frequency range of ECG signals. The filter exhibits a dynamic range (DR) of 70 dB, an input-referred noise of 34.77 μVrms and a third-order harmonic distortion (HD3) of 65.605 dB at 50 Hz and 50 mV pk-pk input. The proposed filter achieves a superior figure of merit (FOM) compared to existing state-of-the-art nano-power filters, providing an optimal balance between power consumption, linearity, and noise performance, making it a highly effective solution for wearable health care monitoring devices.