7.2 nW 68 dB DR Fourth Order Self-compensated Low Pass Filter for Portable ECG Application

This paper describes the designing of a fourth order low-pass filter (LPF) for portable ECG application. The proposed filter is designed by cascading one P-biquad and one N-biquad to form a fourth order filter. It is self-compensated and provides a 0 dB gain. It also acquires the same input and output common mode voltages, which helps to produce higher order filters. It consumes power of 7.2 nW with a supply voltage of 1.2 V. Dynamic range of 68.1 dB with noise of 61.2 mu Vrms is obtained. The proposed filter is designed for a cut-off frequency of 230 Hz, suitable for ECG application. With 100 Hz frequency and 100 mV(pp) ac amplitude, HD3 of 71 dB is achieved. The circuit is simulated in cadence software using Silterra 130 nm CMOS technology. Compared with other state-of-the-art designs, this novel LPF provides the largest dynamic range and the best figure of merit (FOM).