INCREASING THE COMMON-MODE REJECTION RATIO  OF THE DIFFERENTIAL SIGNAL EXTRACTION BLOCK IN THE STRUCTURE OF THE LOCK-IN AMPLIFIER

Bùi Đức Biên

doi:10.34238/tnu-jst.11827

INCREASING THE COMMON-MODE REJECTION RATIO OF THE DIFFERENTIAL SIGNAL EXTRACTION BLOCK IN THE STRUCTURE OF THE LOCK-IN AMPLIFIER

About this article

Received: 07/01/25 Revised: 28/03/25 Published: 03/04/25

Authors

Bui Duc Bien , 1) Institute of Technology - General Department of Military Industries and Manufacture, 2) School of Non-Destructive Testing - Tomsk Polytechnic University

Abstract

When measuring electrical and magnetic quantities, lock-in amplifiers are widely used to determine microvolt-range alternating voltage values superimposed on significantly large common mode noise. Currently, no commercial lock-in amplifier achieves a common-mode rejection ratio of 180 dB up to 1 kHz for AC voltages of 10√2 V. These measurement parameters of the lock-in amplifier are typically determined by the differential signal extraction block at the device’s input. This study aims to enhance the common mode rejection ratio and extend the voltage comparison range by optimizing the structure of differential signal extraction block. This involves utilizing an instrumentation amplifier chip; designing, fabricating and powering a dedicated tracking power supply. The improved design enables comparison of 10√2 alternating voltages, achieving 180 dB common mode rejection ratio up to 1 kHz. The results of the research have been applied in the fabrication of a lock-in amplifier, which is used in practice at metrology and research facilities.

Keywords

Tracking power supply; Lock-in amplifier; Instrumentation amplifier; Voltage follower; Common mode rejection ratio

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DOI: https://doi.org/10.34238/tnu-jst.11827

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