Lock-in amplifier for portable sensing systems

Presented is a 3 V single supply analogue lock-in amplifier designed for processing output sensor signals in highly noisy environments. The proposed amplifier uses square input signals instead of the usual sinusoidal signals, consequently allowing a straight interface with microcontroller-based sensing systems working with both resistive and capacitive transducers. Experimental results for noisy signals with DC voltage variation confirm the capability of the proposed solution to effectively recover information from signal-to-noise ratios down to -24 dB with errors below 6% and with an average power consumption of only 5 mW in full operation.