An analog lock-in amplifier for embedded sensor electronic interfaces

This paper presents a single supply analog lock-in amplifier for processing sensor noisy signals in low-voltage low-power embedded applications. The proposed system is based on a dual channel architecture to eliminate the phase dependence and enable its use for both resistive and capacitive sensors. In addition, looking for a compact solution, instead of a sinusoidal input a square wave input which can be directly obtained from one of the outputs of the embedded microcontroller is considered. Experimental results for tests conducted with white noise, flicker noise, interference contamination and common-mode voltage contamination confirm the capability of the proposed amplifier to effectively recover information from signal to noise ratios below -24dB with errors below 6%.