A 1.7nW 24 Hz Variable Gain Elliptic Low Pass Filter in 90-nm CMOS for Biosignal Detection

摘要

This paper presents a fourth-order elliptic low pass filter for the detection of biopotential signals. The filter has a bandwidth of 24 Hz to be used for the acquisition of Electroencephalogram (EEG) and Electrocardiogram (ECG). An embedded variable gain amplifier provides the filter with variable gain ranging from 0.39 dB to 18 dB. A single notch is positioned at frequency 50 Hz to eliminate the power-line interference signal, with an attenuation of 51 dB achieved. The proposed OTA-C filter structure is simulated in LTspice using 90 nm CMOS model BSIM4 (level 54) under ± 0.6 V voltage supply. The proposed filter has an input referred noise spectral density of 19.6 pV/Hz½ at 10 Hz at DC gain 18 dB. The total harmonic distortion (THD) is 2.45% for a sinusoidal input of 10 mV, 5Hz at DC gain of 6.6 dB. The standby power consumption of the filter ranges between 1.5n nW at a gain of 0.39 dB and 1.7 nW at gain of 18 dB.