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 mu m 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 mu W 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.