Modified Current-reuse OTA to Achieve High CMRR by utilizing Cross-coupled Load

Since biomedical signals have very low amplitude and high common-mode like environmental noise, the amplifiers used with these signals should have high CMRR. The cross-coupled amplifier attenuates common-mode signal strongly because of its load behavior for differential and common-mode signal which leads to high CMRR. Since cross-coupled amplifier differential gain is low, its load is combined with current-reuse operational amplifier. The final CMRR of a fully differential current-reuse OTA with conventional common-mode feedback and modified load is simulated and compared in a 0.18 μm CMOS technology. Their CMRR is simulated for mismatch and process variation. According to the simulation, for the same power consumption, W and L, the modified current-reuse with cross-coupled load has the best performance. Its CMRR in the worst case was about 90 dB while the total power consumption was 18 μW at 1.8 V supply voltage. The Bandwidth is 4.8 kHz and the total input referred noise in this bandwidth is 1.04 μV
_rms
and 0.43 μV
_rms
from 0.5 to 100 Hz which is acceptable noise and bandwidth for the EEG application considered in this study.