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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 mm2. The LIA performance was demonstrated by measuring carbon monoxide concentrations as low as 1 ppm in dry N2. The experimental results show that the response to CO of the sensing system can be considerably improved by means of the proposed LIA.

For current microelectronic integrated systems, the design methodology involves different steps that end up in the full system simulation by means of electrical and physical models prior to its manufacture. However, the higher the circuit complexity, the more time is required to complete these simulations, jeopardizing the convergence of the numerical methods and, hence, meaning that the reliability of the results are not guaranteed. This paper shows the use of a high-level tool based on Matlab to simulate the operation of an artificial neural network implemented in a mixed analog-digital CMOS process, intended for sensor calibration purposes. The proposed standard tool enables modification of the neural model architecture to adapt its characteristics to those of the electronic system, resulting in accurate behavioral models that predict the complete microelectronic IC system behavior under different operation conditions before its physical implementation with a simple, time-efficient, and reliable solution.

This paper presents the design and experimental characterization of two lock-in amplifier (LIA) prototypes integrated in a 0.18-µm CMOS process with a single supply voltage of 1.8 V. As opposed to previously reported integrated LIAs, synchronous rectification is performed in the current domain, providing key features such as low power (<420 µW) and reduced area (0.013 mm 2 ), with a dynamic reserve better than 35 dB and less than 5% relative error in the signal recovery. The principle of operation of each prototype is presented and their performance is compared with previous implementations, validating their suitability for low-cost portable applications.Index Terms-Analog integrated design, analog processing circuits, lock-in amplifiers (LIAs), low-voltage low-power, programmable circuits.

The design and experimental characterization of a high-resolution analog lock-in amplifier (LIA)-based measurement system is presented in this paper. Different design strategies are used to attain a versatile solution which features programmable gain (72.6 -82.6 dB) and operating frequency (5 -115 kHz), preserving good recovery performance. The prototype, integrated in the UMC 0.18 µm CMOS process with a single supply voltage of 1.8 V, achieves a resolution of 200 nV and a high dynamic reserve of 43.5 dB, showing significantly lower power consumption (885 µW) than high-resolution state-of-the-art LIAs with minimum size (0.075 mm 2 silicon area). To validate the amplitude recovery performance of the proposed single-phase LIA, it was used to measure the equivalent value of a passive resistive sensor, exhibiting a maximum error of 1.9 % when RS is varied from 100 Ω to 10 kΩ with an input signal in the order of hundreds of microvolts. Thus, it constitutes a highly suitable choice for portable and lab-on-a-chip sensing applications.