A 400 $\mu$ W Hz-Range Lock-In A/D Frontend Channel for Infrared Spectroscopic Gas Recognition

This paper presents a low-power and fully integrated frontend channel for long-wave infrared spectroscopic gas recognition. The proposed channel circuitry includes: input sensor biasing, sub-Hz high-pass filtering and pre-amplification, differential blind cancellation, and lock-in A/D conversion. The proposed CMOS circuits make extensive use of transistor subthreshold operation and digital programmability. Experimental results are presented for a 0.3 mm
²
400 μW channel prototype integrated in 0.35 μm CMOS technology.