A 0.5 V 60 nW fully-differential log-domain band-pass filter with tunable cutoff frequency for biosensor applications

Abstract

This paper presents a new architecture to implement an analogue continues-time band-pass filter (BPF) with tunable cutoff frequency by employing the log-domain principle for low voltage biosensor applications. The new proposal is based on the analytical description of MOS transistor models in subthreshold regime. The fully-differential BPF is implemented by using two log-domain low-pass filters (LPFs) with different time constants. Meanwhile, a voltage-current converter with good linear performance is also integrated for weak voltage signal conditioning. All these blocks operate in a 0.5 V supply voltage without degrading of the dynamic range and noise performance. The core circuit of the BPF occupies an active area of 0.032 mm2 in a 180 nm standard CMOS process. Post-simulation results show that the BPF has a wide range of cutoff frequencies, which can be tuned from 1 mHz to 10 kHz. The integrated root-mean-square (RMS) of input-referred noise current is 87.8 pArms in the frequency range of 1m Hz to 10 kHz, and the power consumption is only 60 nW at a single 0.5 V supply voltage.