An Integrated Low-Power Lock-In Amplifier and Its Application to Gas Detection

This paper presents a new micropower analog lock-in amplifier (LIA) suitable for battery-operated applications thanks to its reduced size and power consumption as well as its operation with single-supply voltage. The proposed LIA was designed in a 0.18 μm CMOS process with a single supply voltage of 1.8 V. Experimental results show a variable DC gain ranging from 24.7 to 42 dB, power consumption of 417 μW and integration area of 0.013 mm(2). The LIA performance was demonstrated by measuring carbon monoxide concentrations as low as 1 ppm in dry N(2). The experimental results show that the response to CO of the sensing system can be considerably improved by means of the proposed LIA.