Fast and effective method of CMRR enhancement for multichannel integrated circuits dedicated to biomedical measurements

The common mode rejection ratio (CMRR) strongly depends on matching and this effect is clearly visible in multichannel recording systems. Therefore, a method for improving the CMRR in multichannel recording integrated circuits (ICs) dedicated to biomedical experiments is reported. The method is based on balancing the amplifier´s inputs using leakage currents. The proposed technique was verified in the 64 channel IC processed in CMOS 180 nm. The measurement results show that with use of the proposed balancing technique the CMRR is increased by more than 30 dB. Additionally, in comparison to conventional CMRR measurement methods, the proposed solution is attractive in three ways: its on-chip implementation simplicity, fast operation, and it is especially suitable for modern nanometre processes.