A 100/μA/Ch fully-integrable lock-in multi-channel frontend for infrared spectroscopic gas recognition

This paper presents a low-power and fully-integrable multichannel digital read-out integrated circuit for infrared spectroscopic gas recognition. The proposed channel circuitry includes: sensor biasing, sub-Hz high-pass filtering and pre-amplification, blind cancellation, lock-in demodulation, and A/D conversion, all together with independent programmability and thermal compensation. The proposed CMOS circuits make extensive use of transistor subthreshold operation and circuit reuse. Experimental results are presented for a 300μm×715μm channel prototype integrated in 0.35μm CMOS technology.