Increasing common-mode rejection ratio based on the voltage follower

Abstract

The paper presents certain procedures oriented towards the decrease of the uncertainty of measuring the small differential signal against a large common-mode signal. The technical implementation of the tracking symmetrical power supply is suggested for the instrumentation amplifier based on the voltage follower that allows increasing the common mode rejection ratio and input impedance and decreasing the cable capacitance. Keywords-voltage divider; lock-in amplifier with a differential input; common-mode rejection ratio

Dual Phase Lock-In Amplifier with Photovoltaic Modules and Quasi-Invariant Common-Mode Signal

“…As can be seen from Table 1, the real resolution of modern lock-in amplifiers is restricted by 100-120 dB CMRR of the input instrumentation amplifier, while their maximum input voltage does not exceed 1 V, which is insufficient for, for example, metrological support of state-of-the-art measuring instruments, which requires comparing RMS voltages of ≤10 V with a resolution in units of nanovolts. The analysis of errors produced by the main units (see Figure 1) given in our early research [43] shows that the resolution of lock-in amplifiers is mostly affected by the common-mode signal of the input instrumentation amplifier. The development of solutions is, therefore, required to increase the CMRR and develop lock-in amplifiers with quasiinvariant common-mode signal.…”

“…Figure 2 shows the schematic circuit of the differential signal recovery based on the voltage follower, which utilizes this principle for the CMRR increase. The analysis of errors produced by the main units (see Figure 1) given in our early research [43] shows that the resolution of lock-in amplifiers is mostly affected by the common-mode signal of the input instrumentation amplifier. The development of solutions is, therefore, required to increase the CMRR and develop lock-in amplifiers with quasi-invariant common-mode signal.…”