Circuits for differential signal extraction in the lock-in amplifiers

Confirmation of the metrological characteristics of measuring transducers provides maximum accuracy of the method of comparison with the standard instrument. Practical application of this technique is impossible without accurate instruments. As a measurement instrument to ensure the resolution of the order of several nanovolts when comparing two AC signals over a wide dynamic range, widely used lock-in amplifier with a differential input. The paper presents the results of the analysis of circuits based on operational amplifiers for comparing two signals and extraction differential signal in lock-in amplifier with a differential input. Common-mode rejection ratio for each of the circuits was estimated.