0.279 nW fourth-order filter circuit for biological signal conditioning

In this article, a fourth-order low-pass filter (LPF) is designed and analyzed for wearable biological healthcare applications. The proposed LPF is based on level shifter, class-AB folded flipped source follower, and pseudo-resistive voltage-variative approaches, which increases its power efficiency. The proposed LPF consumes 0.279 nW of power with a figure of merit of 2.13 × 10−15 J in CMOS 180 nm process. Furthermore, the post-layout simulations executed for the proposed LPF show a gain of −0.126 dB, a bandwidth of 100 Hz, total harmonic distortion (THD) of −48.53 dB, and a dynamic range (DR) of 50.19 dB. In addition to this, the Monte Carlo simulations with 200 samples demonstrate the corresponding mean and standard deviation values for gain (−0.282 and 0.517 dB), DR (50.18 and 0.025 dB), and THD (−46.175 and 3.258 dB). The proposed fourth-order LPF is a perfect match for wearable biological healthcare systems that are portable and safe.