14.4 nW fourth-order bandpass filter for biomedical applications

A bandpass biquad with ultra low power consumption suitable for biomedical applications is proposed. In this biquad, one zero and two complex poles are synthesised in a single differential stage. An all-PMOS fourth-order Butterworth prototype comprising two such biquads has been fabricated in 0.18 μm CMOS process. The measured passband is from 523 to 1024 HZ, and it consumes only 14.4 nA under 1.0 V supply voltage. 1% THD is achieved with 80 mVpp input, along with 50 μVrms input-referred noise yielding a dynamic range of 55 dB.